-<HTML>
-<HEAD>
-<TITLE>PostgreSQL FAQ</title>
-</HEAD>
-<BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#FF0000" VLINK="#A00000" ALINK="#0000FF">
-<H1>
-Frequently Asked Questions (FAQ) for PostgreSQL
-</H1>
-<P>
-Last updated: Wed Jun 11 10:44:40 EDT 1997
-<BR>
-Version: 6.1
-<P>
-Current maintainer: Bruce Momjian (<a
-href="mailto:maillist@candle.pha.pa.us">maillist@candle.pha.pa.us</a>)<BR>
-<P>
-The most recent version of this document can be viewed at
-the postgreSQL Web site, <a
-href="http://postgreSQL.org">http://postgreSQL.org</a>.
-<P>
-Linux-specific questions are answered in
-<a href="http://postgreSQL.org/docs/FAQ-Linux.phtml">http://postgreSQL.org/docs/FAQ-Linux.phtml</a>.
-<P>
-Irix-specific questions are answered in
-<a href="http://postgreSQL.org/docs/FAQ-Irix.phtml">http://postgreSQL.org/docs/FAQ-Irix.phtml</a>.
-<P>
-Changes in this version (* = modified, + = new):
-<UL>
-<LI>3.42) What is Genetic Query Optimization?<BR>
-<LI>3.43) I am running Solaris and my dates display wrong. Why?<BR>
-</UL>
-<HR>
-<P>
-<H2>Questions answered:</H2>
-<H3> 1) General questions</H3>
-<a href="#1.1">1.1</a>) What is PostgreSQL?<BR>
-<a href="#1.2">1.2</a>) What does PostgreSQL run on?<BR>
-<a href="#1.3">1.3</a>) Where can I get PostgreSQL?<BR>
-<a href="#1.4">1.4</a>) What's the copyright on PostgreSQL?<BR>
-<a href="#1.5">1.5</a>) Support for PostgreSQL<BR>
-<a href="#1.6">1.6</a>) Latest release of PostgreSQL<BR>
-<a href="#1.7">1.7</a>) Is there a commercial version of PostgreSQL?<BR>
-<a href="#1.9">1.9</a>) What version of SQL does PostgreSQL use?<BR>
-<a href="#1.10">1.10</a>) Does PostgreSQL work with databases from
-earlier versions of postgres?<BR>
-<a href="#1.11">1.11</a>) How many people use PostgreSQL?<BR>
-<H3> 2) Installation questions</H3>
-<a href="#2.1">2.1</a>) initdb doesn't run<BR>
-<a href="#2.2">2.2</a>) when I start up the postmaster, I get
- "FindBackend: could not find a backend to execute..."
- "postmaster: could not find backend to execute..."<BR>
-<a href="#2.3">2.3</a>) The system seems to be confused about commas,
-decimal points, and date formats.<BR>
-<a href="#2.4">2.4</a>) How do I install PostgreSQL somewhere other than
-/usr/local/pgsql?<BR>
-<a href="#2.5">2.5</a>) When I run postmaster, I get a Bad System Call
-core dumped message.<BR>
-<a href="#2.6">2.6</a>) When I try to start the postmaster, I get
-IpcMemoryCreate errors.<BR>
-<a href="#2.7">2.7</a>) I have changed a source file, but a
-recompile does not see the change?<BR>
-<H3> 3) Operational questions</H3>
-<a href="#3.1">3.1</a>) How do I specify a KEY or other constraints on a
-column?<BR>
-<a href="#3.2">3.2</a>) Does PostgreSQL support nested subqueries?<BR>
-<a href="#3.3">3.3</a>) How do I define a unique indices?<BR>
-<a href="#3.4">3.4</a>) I've having a lot of problems using rules.<BR>
-<a href="#3.5">3.5</a>) I can't seem to write into the middle of large
-objects reliably.<BR>
-<a href="#3.6">3.6</a>) Does PostgreSQL have a graphical user interface?
-A report generator? A embedded query language interface?<BR>
-<a href="#3.7">3.7</a>) How can I write client applications to
-PostgreSQL?<BR>
-<a href="#3.8">3.8</a>) How do I prevent other hosts from accessing my
-PostgreSQL<BR>
-<a href="#3.9">3.9</a>) How do I set up a pg_group?<BR>
-<a href="#3.10">3.10</a>) What is the exact difference between
-binary cursors and normal cursors?<BR>
-<a href="#3.11">3.11</a>) Why doesn't the != operator work?<BR>
-<a href="#3.12">3.12</a>) What is a R-tree index and what is it
-used for?<BR>
-<a href="#3.13">3.13</a>) What is the maximum size for a
-tuple?<BR>
-<a href="#3.14">3.14</a>) I defined indices but my queries don't
-seem to make use of them. Why?<BR>
-<a href="#3.15">3.15</a>) Are there ODBC drivers for
-PostgreSQL?<BR>
-<a href="#3.16">3.16</a>) How do I use postgres for
-multi-dimensional indexing (> 2 dimensions)?<BR>
-<a href="#3.17">3.17</a>) How do I do regular expression searches?
-case-insensitive regexp searching?<BR>
-<a href="#3.18">3.18</a>) I can't access the database as the
-'root' user.<BR>
-<a href="#3.19">3.19</a>) I experienced a server crash during a
-vacuum. How do I remove the lock file?<BR>
-<a href="#3.20">3.20</a>) What is the difference between the
-various character types?<BR>
-<a href="#3.21">3.21</a>) In a query, how do I detect if a field
-is NULL?<BR>
-<a href="#3.22">3.22</a>) How do I see how the query optimizer is
-evaluating my query?<BR>
-<a href="#3.23">3.23</a>) How do I create a serial field?<BR>
-<a href="#3.24">3.24</a>) How do I create a multi-column
-index?<BR>
-<a href="#3.25">3.25</a>) What are the temp_XXX files in my
-database directory?<BR>
-<a href="#3.26">3.26</a>) Why are my table files not getting any
-smaller after a delete?<BR>
-<a href="#3.27">3.27</a>) Why can't I connect to my database from
-another machine?<BR>
-<a href="#3.28">3.28</a>) I get the error 'default index class
-unsupported' when creating an index. How do I do it?<BR>
-<a href="#3.29">3.29</a>) Why does creating an index crash the
-backend server?<BR>
-<a href="#3.30">3.30</a>) How do I find out what indexes or
-operations are defined in the database?<BR>
-<a href="#3.31">3.31</a>) Why do statements require an extra character at
-the end? Why does 'createuser' return 'unexpected last match in
-input()'? Why does pg_dump fail?<BR>
-<a href="#3.32">3.32</a>) All my servers crash under concurrent
-table access. Why?<BR>
-<a href="#3.33">3.33</a>) What tools are available for hooking
-postgres to Web pages?<BR>
-<a href="#3.34">3.34</a>) What is the time-warp feature and how
-does it relate to vacuum?<BR>
-<a href="#3.35">3.35</a>) How do I tune the database engine for
-better performance?<BR>
-<a href="#3.36">3.36</a>) What debugging features are available in
-PostgreSQL?<BR>
-<a href="#3.37">3.37</a>) What is an oid? What is a tid?<BR>
-<a href="#3.38">3.38</a>) What is the meaning of some of the terms
-used in Postgres?<BR>
-<a href="#3.39">3.39</a>) What is Genetic Query Optimization?<BR>
-<a href="#3.40">3.40</a>) I am running Solaris and my dates
-display wrong. Why?
-<a href="#3.41">3.41</a>) How do I enable more than 32 concurrent
-backends?
-<H3> 4) Questions about extending PostgreSQL</H3>
-<a href="#4.1">4.1</a>) I wrote a user-defined function and when I run
-it in psql, it dumps core.<BR>
-<a href="#4.2">4.2</a>) I get messages of the type
-NOTICE:PortalHeapMemoryFree: 0x402251d0<BR>
-<a href="#4.3">4.3</a>) I've written some nifty new types and functions
-for PostgreSQL.<BR>
-<a href="#4.4">4.4</a>) How do I write a C function to return a
-tuple?<BR>
-<H3> 5) Bugs</H3>
-<a href="#5.1">5.1</a>) How do I make a bug report?
-<HR> <H2> Section 1: General Questions</H2> <H3><a
-name="1.1">1.1</a>) What is PostgreSQL?</H3>
+ Frequently Asked Questions (FAQ) for PostgreSQL
+
+ Last updated: Sun Jul 13 15:26:53 EDT 1997
+ Version: 6.1.1
+
+ Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us)
+
+ The most recent version of this document can be viewed at the
+ postgreSQL Web site, http://postgreSQL.org.
+
+ Linux-specific questions are answered in
+ http://postgreSQL.org/docs/FAQ-Linux.phtml.
+
+ Irix-specific questions are answered in
+ http://postgreSQL.org/docs/FAQ-Irix.phtml.
+
+ Changes in this version (* = modified, + = new):
+ * 3.42) What is Genetic Query Optimization?
+ * 3.43) I am running Solaris and my dates display wrong. Why?
+
+ _________________________________________________________________
+
+Questions answered:
-<P>
-PostgreSQL is an enhancement of the POSTGRES database management system,
-a next-generation DBMS research prototype. While PostgreSQL retains the
-powerful data model and rich data types of POSTGRES, it replaces the
-PostQuel query language with an extended subset of SQL. PostgreSQL is
-free and the complete source is available.
-<P>
-PostgreSQL development is being performed by a team of Internet
-developers who all subscribe to the PostgreSQL development mailing list.
-The current coordinator is Marc G. Fournier (<a
-href="mailto:scrappy@postgreSQL.org">scrappy@postgreSQL.org</a>). (See
-below on how to join). This team is now responsible for all current and
-future development of PostgreSQL.
-<P>
-The authors of PostgreSQL 1.01 were Andrew Yu and Jolly Chen. Many
-others have contributed to the porting, testing, debugging and
-enhancement of the code. The original Postgres code, from which
-PostgreSQL is derived, was the effort of many graduate students,
-undergraduate students, and staff programmers working under the
-direction of Professor Michael Stonebraker at the University of
-California, Berkeley.
-<P>
-The original name of the software at Berkeley was Postgres. When SQL
-functionality was added in 1995, its name was changed to Postgres95. The
-name was changed at the end of 1996 to PostgreSQL.
-<P>
-<H3><a name="1.2">1.2</a>) What does PostgreSQL run
-on?</H3>
-<P>
-The authors have compiled and tested PostgreSQL on the following
-platforms(some of these compiles require gcc 2.7.0):
-<UL>
-<LI> aix - IBM on AIX 3.2.5
-<LI> alpha - DEC Alpha AXP on OSF/1 2.0
-<LI> BSD44_derived - OSs derived from 4.4-lite BSD (NetBSD, FreeBSD)
-<LI> bsdi - BSD/OS 2.0, 2.01, 2.1, 3.0
-<LI> dgux - DG/UX 5.4R3.10
-<LI> hpux - HP PA-RISC on HP-UX 9.0
-<LI> i386_solaris - i386 Solaris
-<LI> irix5 - SGI MIPS on IRIX 5.3
-<LI> linux - Intel x86 on Linux 1.2 and Linux ELF
- (For non-ELF Linux, see LINUX_ELF below).
-<LI> sparc_solaris - SUN SPARC on Solaris 2.4
-<LI> sunos4 - SUN SPARC on SunOS 4.1.3
-<LI> svr4 - Intel x86 on Intel SVR4
-<LI> ultrix4 - DEC MIPS on Ultrix 4.4
-</UL>
-The following platforms have known problems/bugs:
-<UL>
-<LI> nextstep - Motorola MC68K or Intel x86 on NeXTSTEP 3.2
-</UL>
-<P>
-<H3><a name="1.3">1.3</a>) Where can I get PostgreSQL?</H3>
-<P> The primary anonymous ftp site for PostgreSQL is:
-<UL>
-<LI> <a
-href="ftp://ftp.postgreSQL.org/pub">ftp://ftp.postgreSQL.org/pub</a>
-</UL>
-<P> A mirror site exists at:
-<UL>
-<LI> <a
-href="ftp://postgres95.vnet.net/pub/postgres95">ftp://postgres95.vnet.net/pub/postgres95</a>
-<LI> <a
-href="ftp://ftp.luga.or.at/pub/postgres95">ftp://ftp.luga.or.at/pub/postgres95</a>
-<LI> <a
-href="ftp://cal011111.student.utwente.nl/pub/postgres95">ftp://cal011111.student.utwente.nl/pub/postgres95</a>
-<LI> <a
-href="ftp://ftp.uni-trier.de/pub/database/rdbms/postgres/postgres95">ftp://ftp.uni-trier.de/pub/database/rdbms/postgres/postgres95</a>
-<LI> <a
-href="ftp://rocker.sch.bme.hu">ftp://rocker.sch.bme.hu</a>
-</UL>
-<H3><a name="1.4">1.4</a>) What's the copyright on
-PostgreSQL?</H3>
-<P>
-PostgreSQL is subject to the following COPYRIGHT.
-<P>
-PostgreSQL Data Base Management System
-<P>
-Copyright (c) 1994-6 Regents of the University of California
-<P>
-Permission to use, copy, modify, and distribute this software and its
-documentation for any purpose, without fee, and without a written
-agreement is hereby granted, provided that the above copyright notice
-and this paragraph and the following two paragraphs appear in all
-copies.
-<P>
-IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
-FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
-INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
-DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF
-THE POSSIBILITY OF SUCH DAMAGE.
-<P>
-THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
-INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
-AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER
-IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO
-OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR
-MODIFICATIONS.
-<P>
-<H3><a name="1.5">1.5</a>) Support for PostgreSQL </H3>
-<P>
-There is no official support for PostgreSQL from the original
-maintainers or from University of California, Berkeley. It is
-maintained through volunteer effort only.
-<P>
-The main mailing list is: <a
-href="mailto:questions@postgreSQL.org">questions@postgreSQL.org</a>. It
-is available for discussion o f matters pertaining to PostgreSQL,
-including but not limited to bug reports and fixes. For info on how to
-subscribe, send a mail with the lines in the body (not the subject line)
-<PRE>
-<CODE>
- subscribe
- end
-</CODE>
-</PRE>
-<P>
-to <a
-href="mailto:questions-request@postgreSQL.org">questions-request@postgreSQL.org</a>.
-<P>
-There is also a digest list available. To subscribe to this list, send
-email to:
-<a
-href="mailto:questions-digest-request@postgreSQL.org">
-questions-digest-request@postgreSQL.org</a> with a BODY of:
-<PRE>
-<KBD>
- subscribe
- end
-</KBD>
-</PRE>
-Digests are sent out to members of this list whenever the main list has
-received around 30k of messages.
-<P>
-There is a bugs mailing list available. To subscribe to this
-list, send email to <a
-href="mailto:bugs-request@postgreSQL.org">bugs-request@postgreSQL.org</a>
-with a BODY of:
-<P>
-There is also a developers discussion mailing list available. To subscribe to this
-list, send email to <a
-href="mailto:hackers-request@postgreSQL.org">hackers-request@postgreSQL.org</a>
-with a BODY of:
-<P>
-<PRE>
-<KBD>
- subscribe
- end
-</KBD>
-</PRE>
-<P>
-Additional information about PostgreSQL can be found via the PostgreSQL
-WWW home page at:
-<BLOCKQUOTE>
- <a
-href="http://postgreSQL.org">http://postgreSQL.org</a>
-</BLOCKQUOTE>
-<P>
-<H3><a name="1.6">1.6</a>) Latest release of PostgreSQL</H3>
-<P>
-The latest release of PostgreSQL is version 6.0, which was released on
-January 31, 1997. 6.1 is scheduled for release soon. For information
-about what is new in 6.1, see our TODO list on our WWW page.
-<P>
-We expect a 7.0 release in several months that will remove time-travel
-and reduce by 50% the size of on-disk system columns maintained for each
-row in a table. This release will also require a dump and restore.
-<P>
-<H3><a name="1.7">1.7</a>) Is there a commercial version of PostgreSQL?</H3>
-<P>
-Illustra Information Technology (a wholly owned subsidiary of Informix
-Software, Inc.) sells an object-relational DBMS called Illustra that was
-originally based on postgres. Illustra has cosmetic similarities to
-PostgreSQL but has more features, is more robust, performs better, and
-offers real documentation and support. On the flip side, it costs
-money. For more information, contact <a
-href="mailto:sales@illustra.com">sales@illustra.com</a>
-<P>
-<H3><a name="1.8">1.8</a>) What documentation is available for PostgreSQL?</H3>
-<P>
-A user manual, manual pages, and some small test examples are included
-in the distribution. The sql and built-in manual pages are particularly
-important.
-<P>
-The www page contains pointers to an implementation guide and five
-papers written about postgres design concepts and features.
-<P>
-<H3><a name="1.9">1.9</a>) What version of SQL does PostgreSQL use?</H3>
-<P>
-PostgreSQL supports a subset of SQL-92. It has most of the important
-constructs but lacks some of the functionality. The most visible
-differences are:
-<UL>
-<LI> no support for nested subqueries
-<LI> no HAVING clause under a GROUP BY
-</UL>
-<P>
-On the other hand, you get to create user-defined types, functions,
-inheritance etc. If you're willing to help with PostgreSQL coding,
-eventually we can also add the missing features listed above.
-<P>
-<H3><a name="1.10">1.10</a>) Does PostgreSQL work with databases from
-earlier versions of postgres?</H3>
-<P>
-PostgreSQL v1.09 is compatible with databases created with v1.01. Those
-upgrading from 1.0 should read the directions in the
-MIGRATION_1.0_TO_1.02 directory.
-<P>
-Upgrading to 6.0 requires a dump and restore from previous releases.
-<P>
-Upgrading to 6.1 requires a dump and restore from previous releases.
-<P>
-Those ugrading from versions earlier than 1.09 must upgrade to 1.09
-first without a dump/reload, then dump the data from 1.09, and then load
-it into 6.0 or 6.1.
-<P>
-<H3><a name="1.11">1.11</a>) How many people use PostgreSQL?</H3>
-<P>
-Since we don't have any licensing or registration scheme, it's
-impossible to tell. We do know hundreds copies of PostgreSQL v1.* have
-been downloaded, and that there many hundreds of subscribers to the
-mailing lists.
-<P>
-<HR>
-<H2> Section 2: Installation Questions
-</H2>
-<P>
-<H3><a name="2.1">2.1</a>) initdb doesn't run</H3>
-<P>
-<UL>
-<LI> check to see that you have the proper paths set
-<LI> check that the 'postgres' user owns all the right files
-<LI> ensure that there are files in $PGDATA/files, and that they
-are non-empty. If they aren't, then "gmake install" failed for
-some reason
-</UL>
-<P>
-<H3><a name="2.2">2.2</a>) when I start up the postmaster, I get
- "FindBackend: could not find a backend to execute..."
- "postmaster: could not find backend to execute..."</H3>
-<P>
-You probably do not have the right path set up. The 'postgres'
-executable needs to be in your path.
-<P>
-<H3><a name="2.3">2.3</a>) The system seems to be confused about commas,
-decimal points, and date formats.</H3>
-<P>
-Check your locale configuration. PostgreSQL uses the locale settings of
-the user that ran the postmaster process. Set those accordingly for
-your operating environment.
-<P>
-<H3><a name="2.4">2.4</a>) How do I install PostgreSQL somewhere other than
-/usr/local/pgsql?</H3>
-<P>
-You need to edit Makefile.global and change POSTGRESDIR accordingly, or
-create a Makefile.custom and define POSTGRESDIR there.
-<P>
-<H3><a name="2.5">2.5</a>) When I run postmaster, I get a Bad System
-Call core dumped message.</H3>
-<P>
-It could be a variety of problems, but first check to see that you have
-system V extensions installed on your kernel. PostgreSQL requires kernel
-support for shared memory.
-<P>
-<H3><a name="2.6">2.6</a>) When I try to start the postmaster, I get
-IpcMemoryCreate errors.</H3>
-<P>
-You either do not have shared memory configured properly in kernel or
-you need to enlarge the shared memory available in the kernel. The
-exact amount you need depends on your architecture and how many buffers
-you configure postmaster to run with. For most systems, with default
-buffer sizes, you need a minimum of ~760K.
-<P>
-<H3><a name="2.7">2.7</a>) I have changed a source file, but a
-recompile does not see the change?</H3>
-<P>
-The Makefiles do not have the proper dependencies for include files. You
-have to do a 'make clean' and then another 'make'.
-<P>
-<HR>
-<H2> Section 3: PostgreSQL Features
-</H2>
+ 1) General questions
+
+ 1.1) What is PostgreSQL?
+ 1.2) What does PostgreSQL run on?
+ 1.3) Where can I get PostgreSQL?
+ 1.4) What's the copyright on PostgreSQL?
+ 1.5) Support for PostgreSQL
+ 1.6) Latest release of PostgreSQL
+ 1.7) Is there a commercial version of PostgreSQL?
+ 1.9) What version of SQL does PostgreSQL use?
+ 1.10) Does PostgreSQL work with databases from earlier versions of
+ postgres?
+ 1.11) How many people use PostgreSQL?
+
+ 2) Installation questions
+
+ 2.1) initdb doesn't run
+ 2.2) when I start up the postmaster, I get "FindBackend: could not
+ find a backend to execute..." "postmaster: could not find backend to
+ execute..."
+ 2.3) The system seems to be confused about commas, decimal points, and
+ date formats.
+ 2.4) How do I install PostgreSQL somewhere other than
+ /usr/local/pgsql?
+ 2.5) When I run postmaster, I get a Bad System Call core dumped
+ message.
+ 2.6) When I try to start the postmaster, I get IpcMemoryCreate errors.
+ 2.7) I have changed a source file, but a recompile does not see the
+ change?
+
+ 3) Operational questions
+
+ 3.1) How do I specify a KEY or other constraints on a column?
+ 3.2) Does PostgreSQL support nested subqueries?
+ 3.3) How do I define a unique indices?
+ 3.4) I've having a lot of problems using rules.
+ 3.5) I can't seem to write into the middle of large objects reliably.
+ 3.6) Does PostgreSQL have a graphical user interface? A report
+ generator? A embedded query language interface?
+ 3.7) How can I write client applications to PostgreSQL?
+ 3.8) How do I prevent other hosts from accessing my PostgreSQL
+ 3.9) How do I set up a pg_group?
+ 3.10) What is the exact difference between binary cursors and normal
+ cursors?
+ 3.11) Why doesn't the != operator work?
+ 3.12) What is a R-tree index and what is it used for?
+ 3.13) What is the maximum size for a tuple?
+ 3.14) I defined indices but my queries don't seem to make use of them.
+ Why?
+ 3.15) Are there ODBC drivers for PostgreSQL?
+ 3.16) How do I use postgres for multi-dimensional indexing (> 2
+ dimensions)?
+ 3.17) How do I do regular expression searches? case-insensitive regexp
+ searching?
+ 3.18) I can't access the database as the 'root' user.
+ 3.19) I experienced a server crash during a vacuum. How do I remove
+ the lock file?
+ 3.20) What is the difference between the various character types?
+ 3.21) In a query, how do I detect if a field is NULL?
+ 3.22) How do I see how the query optimizer is evaluating my query?
+ 3.23) How do I create a serial field?
+ 3.24) How do I create a multi-column index?
+ 3.25) What are the temp_XXX files in my database directory?
+ 3.26) Why are my table files not getting any smaller after a delete?
+ 3.27) Why can't I connect to my database from another machine?
+ 3.28) I get the error 'default index class unsupported' when creating
+ an index. How do I do it?
+ 3.29) Why does creating an index crash the backend server?
+ 3.30) How do I find out what indexes or operations are defined in the
+ database?
+ 3.31) Why do statements require an extra character at the end? Why
+ does 'createuser' return 'unexpected last match in input()'? Why does
+ pg_dump fail?
+ 3.32) All my servers crash under concurrent table access. Why?
+ 3.33) What tools are available for hooking postgres to Web pages?
+ 3.34) What is the time-warp feature and how does it relate to vacuum?
+ 3.35) How do I tune the database engine for better performance?
+ 3.36) What debugging features are available in PostgreSQL?
+ 3.37) What is an oid? What is a tid?
+ 3.38) What is the meaning of some of the terms used in Postgres?
+ 3.39) What is Genetic Query Optimization?
+ 3.40) I am running Solaris and my dates display wrong. Why? 3.41) How
+ do I enable more than 32 concurrent backends?
+
+ 4) Questions about extending PostgreSQL
+
+ 4.1) I wrote a user-defined function and when I run it in psql, it
+ dumps core.
+ 4.2) I get messages of the type NOTICE:PortalHeapMemoryFree:
+ 0x402251d0
+ 4.3) I've written some nifty new types and functions for PostgreSQL.
+ 4.4) How do I write a C function to return a tuple?
+
+ 5) Bugs
+
+ 5.1) How do I make a bug report?
+ _________________________________________________________________
+
+Section 1: General Questions
-<P>
-<H3><a name="3.1">3.1</a>) How do I specify a KEY or other constraints on a
-column?</H3>
-<P>
-Column constraints are not supported in PostgreSQL. As a consequence,
-the system does not check for duplicates.
-<P>
-Under 6.0, create a unique index on the column. Attempts to create
-duplicate of that column will report an error.
-<P>
-<H3><a name="3.2">3.2</a>) Does PostgreSQL support nested subqueries?</H3>
-<P>
-Subqueries are not implemented, but they can be simulated using sql
-functions.
-<P>
-<H3><a name="3.3">3.3</a>) How do I define a unique indices?</H3>
-<P>
-PostgreSQL 6.0 supports unique indices.
-<P>
-<H3><a name="3.4">3.4</a>) I've having a lot of problems using rules.</H3>
-<P>
-Currently, the rule system in PostgreSQL is mostly broken. It works
-enough to support the view mechanism, but that's about it. Use
-PostgreSQL rules at your own peril.
-<P>
-<H3><a name="3.5">3.5</a>) I can't seem to write into the middle of large
-objects reliably.</H3>
-<P>
-The Inversion large object system in PostgreSQL is also mostly broken.
-It works well enough for storing large wads of data and reading them
-back out, but the implementation has some underlying problems. Use
-PostgreSQL large objects at your own peril.
-<P>
-<H3><a name="3.6">3.6</a>) Does PostgreSQL have a graphical user interface?
-A report generator? A embedded query language interface?</H3>
-<P>
-No. No. No. Not in the official distribution at least. Some users have
-reported some success at using 'pgbrowse' and 'onyx' as frontends to
-PostgreSQL. Several contributions are working on tk based frontend
-tools. Ask on the mailing list.
-<P>
-<H3><a name="3.7">3.7</a>) How can I write client applications to PostgreSQL?</H3>
-<P>
-PostgreSQL supports a C-callable library interface called libpq as well
-as a Tcl-based library interface called libtcl.
-<P>
-Others have contributed a perl interface and a WWW gateway to
-PostgreSQL. See the PostgreSQL home pages for more details.
-<P>
-<H3><a name="3.8">3.8</a>) How do I prevent other hosts from accessing my
-PostgreSQL backend?</H3>
-<P>
-Use host-based authentication by modifying the file $PGDATA/pg_hba
-accordingly.
-<P>
-<H3><a name="3.9">3.9</a>) How do I set up a pg_group?</H3>
-<P>
-Currently, there is no easy interface to set up user groups. You have to
-explicitly insert/update the pg_group table. For example:
-<PRE>
-<CODE>
- jolly=> insert into pg_group (groname, grosysid, grolist)
- jolly=> values ('posthackers', '1234', '{5443, 8261}');
- INSERT 548224
- jolly=> grant insert on foo to group posthackers;
- CHANGE
- jolly=>
-</CODE>
-</PRE>
-<P>
- The fields in pg_group are:
-<UL>
-<LI> groname: the group name. This a char16 and should
- be purely alphanumeric. Do not include underscores
- or other punctuation.
-<LI> grosysid: the group id. This is an int4.
- This should be unique for each group.
-<LI> grolist: the list of pg_user id's that belong in the group.
- This is an int4[].
-</UL>
-<P>
-<H3><a name="3.10">3.10</a>) What is the exact difference between binary
-cursors and normal cursors?</H3>
-<P>
-Normal cursors return data back in ASCII format. Since data is stored
-natively in binary format, the system must do a conversion to produce
-the ASCII format. In addition, ASCII formats are often large in size
-than binary format. Once the attributes come back in ASCII, often the
-client application then has to convert it to a binary format to
-manipulate it anyway.
-<P>
-Binary cursors give you back the data in the native binary
-representation. Thus, binary cursors will tend to be a little faster
-since there's less overhead of conversion.
-<P>
-However, ASCII is architectural neutral whereas binary representation
-can differ between different machine architecture. Thus, if your client
-machine uses a different representation than you server machine, getting
-back attributes in binary format is probably not what you want. Also, if
-your main purpose is displaying the data in ASCII, then getting it back
-in ASCII will save you some effort on the client side.
-<P>
-<H3><a name="3.11">3.11</a>) Why doesn't the != operator work?</H3>
-<P>
-SQL specifies <> as the inequality operator, and that is what we
-have defined for the built-in types.
-<P>
-In 6.0, != is equivalent to <>.
-<P>
-<H3><a name="3.12">3.12</a>) What is a R-tree index and what is it used for?</H3>
-<P>
-An r-tree index is used for indexing spatial data. A hash index can't
-handle range searches. A B-tree index only handles range searches in a
-single dimension. R-tree's can handle multi-dimensional data. For
-example, if a R-tree index can be built on an attribute of type 'point',
-the system can more efficient answer queries like select all points
-within a bounding rectangle.
-<P>
-The canonical paper that describes the original R-Tree design is:
-<P>
-Guttman, A. "R-Trees: A Dynamic Index Structure for Spatial Searching."
-Proc of the 1984 ACM SIGMOD Int'l Conf on Mgmt of Data, 45-57.
-<P>
-You can also find this paper in Stonebraker's "Readings in Database
-Systems"
-<P>
-<H3><a name="3.13">3.13</a>) What is the maximum size for a tuple?</H3>
-<P>
-Tuples are limited to 8K bytes. Taking into account system attributes
-and other overhead, one should stay well shy of 8,000 bytes to be on the
-safe side. To use attributes larger than 8K, try using the large
-objects interface.
-<P>
-Tuples do not cross 8k boundaries so a 5k tuple will require 8k of
-storage.
-<P>
-<H3><a name="3.14">3.14</a>) I defined indices but my queries don't seem
-to make use of them. Why?</H3>
-<P>
-PostgreSQL does not automatically maintain statistics. One has to make
-an explicit 'vacuum' call to update the statistics. After statistics
-are updated, the optimizer has a better shot at using indices. Note
-that the optimizer is limited and does not use indices in some
-circumstances (such as OR clauses).
-<P>
-If the system still does not see the index, it is probably because you
-have created an index on a field with the improper *_ops type. For
-example, you have created a CHAR(4) field, but have specified a char_ops
-index type_class.
-<P>
-See the create_index manual page for information on what type classes
-are available. It must match the field type.
-<P>
-Postgres does not warn the user when the improper index is created.
-<P>
-Indexes not used for ORDER BY operations.
-<P>
-<H3><a name="3.15">3.15</a>) Are there ODBC drivers for PostgreSQL?</H3>
-<P>
-There are two ODBC drivers available, PostODBC and OpenLink ODBC.
-<P>
-For all people being interested in PostODBC, there are now two mailing
-lists devoted to the discussion of PostODBC. The mailing lists are:
-<UL>
-<LI> <a
-href="mailto:postodbc-users@listserv.direct.net">postodbc-users@listserv.direct.
-net</a>
-<LI> <a
-href="mailto:postodbc-developers@listserv.direct.net">postodbc-developers@listse
-rv.direct.net</a>
-</UL>
-<P>
-these lists are ordinary majordomo mailing lists. You can subscribe by
-sending a mail to:
-<UL>
-<LI> <a
-href="mailto:majordomo@listserv.direct.net">majordomo@listserv.direct.net</a>
-</UL>
-<P>
-OpenLink ODBC is currently in beta under Linux. You can get it from <a
-href="http://www.openlinksw.com/postgres.html">
-http://www.openlinksw.com/postgres.html</a>. It works with our standard
-ODBC client software so you'll have Postgres ODBC available on every
-client platform we support (Win, Mac, Unix, VMS).
-<P>
-We will probably be selling this product to people who need
-commercial-quality support, but a freeware version will always be
-available. Questions to <a
-href="mailto:postgres95@openlink.co.uk">postgres95@openlink.co.uk</a>.
-<P>
-<H3><a name="3.16">3.16</a>) How do I use postgres for multi-dimensional
-indexing (> 2 dimensions)?</H3>
-<P>
-Builtin R-Trees can handle polygons and boxes. In theory, R-trees can
-be extended to handle higher number of dimensions. In practice,
-extending R-trees require a bit of work and we don't currently have any
-documentation on how to do it.
-<P>
-<H3><a name="3.17">3.17</a>) How do I do regular expression searches?
-case-insensitive regexp searching?</H3>
-<P>
-PostgreSQL supports the SQL LIKE syntax as well as more general regular
-expression searching with the ~ operator. The !~ is the negated regexp
-operator. ~* and !~* are the case-insensitive regular expression
-operators.
-<P>
-<H3><a name="3.18">3.18</a>) I can't access the database as the 'root' user.</H3>
-<P>
-You should not create database users with user id 0(root). They will be
-unable to access the database. This is a security precaution because
-of the ability of any user to dynamically link object modules into the
-database engine.
-<P>
-<H3><a name="3.19">3.19</a>) I experienced a server crash during a
-vacuum. How do I remove the lock file?</H3>
-<P>
-If the server crashes during a vacuum command, chances are it will leave
-a lock file hanging around. Attempts to re-run the vacuum command
-result in
-<PRE>
-<SAMP>
- WARN:can't create lock file -- another vacuum cleaner running?
-</SAMP>
-</PRE>
-<P>
-If you are sure that no vacuum is actually running, you can remove the
-file called "pg_vlock" in your database directory (which is
-$PGDATA/base/<dbName>)
-<P>
-<H3><a name="3.20">3.20</a>) What is the difference between the various
-character types?</H3>
-<PRE>
+ 1.1) What is PostgreSQL?
+
+ PostgreSQL is an enhancement of the POSTGRES database management
+ system, a next-generation DBMS research prototype. While PostgreSQL
+ retains the powerful data model and rich data types of POSTGRES, it
+ replaces the PostQuel query language with an extended subset of SQL.
+ PostgreSQL is free and the complete source is available.
+
+ PostgreSQL development is being performed by a team of Internet
+ developers who all subscribe to the PostgreSQL development mailing
+ list. The current coordinator is Marc G. Fournier
+ (scrappy@postgreSQL.org). (See below on how to join). This team is now
+ responsible for all current and future development of PostgreSQL.
+
+ The authors of PostgreSQL 1.01 were Andrew Yu and Jolly Chen. Many
+ others have contributed to the porting, testing, debugging and
+ enhancement of the code. The original Postgres code, from which
+ PostgreSQL is derived, was the effort of many graduate students,
+ undergraduate students, and staff programmers working under the
+ direction of Professor Michael Stonebraker at the University of
+ California, Berkeley.
+
+ The original name of the software at Berkeley was Postgres. When SQL
+ functionality was added in 1995, its name was changed to Postgres95.
+ The name was changed at the end of 1996 to PostgreSQL.
+
+ 1.2) What does PostgreSQL run on?
+
+ The authors have compiled and tested PostgreSQL on the following
+ platforms(some of these compiles require gcc 2.7.0):
+ * aix - IBM on AIX 3.2.5 or 4.x
+ * alpha - DEC Alpha AXP on OSF/1 2.0
+ * BSD44_derived - OSs derived from 4.4-lite BSD (NetBSD, FreeBSD)
+ * bsdi - BSD/OS 2.0, 2.01, 2.1, 3.0
+ * dgux - DG/UX 5.4R3.10
+ * hpux - HP PA-RISC on HP-UX 9.0
+ * i386_solaris - i386 Solaris
+ * irix5 - SGI MIPS on IRIX 5.3
+ * linux - Intel x86 on Linux 1.2 and Linux ELF (For non-ELF Linux,
+ see LINUX_ELF below).
+ * sparc_solaris - SUN SPARC on Solaris 2.4
+ * sunos4 - SUN SPARC on SunOS 4.1.3
+ * svr4 - Intel x86 on Intel SVR4
+ * ultrix4 - DEC MIPS on Ultrix 4.4
+
+ The following platforms have known problems/bugs:
+ * nextstep - Motorola MC68K or Intel x86 on NeXTSTEP 3.2
+
+ 1.3) Where can I get PostgreSQL?
+
+ The primary anonymous ftp site for PostgreSQL is:
+ * ftp://ftp.postgreSQL.org/pub
+
+ A mirror site exists at:
+ * ftp://postgres95.vnet.net/pub/postgres95
+ * ftp://ftp.luga.or.at/pub/postgres95
+ * ftp://cal011111.student.utwente.nl/pub/postgres95
+ * ftp://ftp.uni-trier.de/pub/database/rdbms/postgres/postgres95
+ * ftp://rocker.sch.bme.hu
+
+ 1.4) What's the copyright on PostgreSQL?
+
+ PostgreSQL is subject to the following COPYRIGHT.
+
+ PostgreSQL Data Base Management System
+
+ Copyright (c) 1994-6 Regents of the University of California
+
+ Permission to use, copy, modify, and distribute this software and its
+ documentation for any purpose, without fee, and without a written
+ agreement is hereby granted, provided that the above copyright notice
+ and this paragraph and the following two paragraphs appear in all
+ copies.
+
+ IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
+ FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
+ INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND
+ ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN
+ ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+ THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
+ INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
+ PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
+ CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT,
+ UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+
+ 1.5) Support for PostgreSQL
+
+ There is no official support for PostgreSQL from the original
+ maintainers or from University of California, Berkeley. It is
+ maintained through volunteer effort only.
+
+ The main mailing list is: questions@postgreSQL.org. It is available
+ for discussion o f matters pertaining to PostgreSQL, including but not
+ limited to bug reports and fixes. For info on how to subscribe, send a
+ mail with the lines in the body (not the subject line)
+
+
+ subscribe
+ end
+
+ to questions-request@postgreSQL.org.
+
+ There is also a digest list available. To subscribe to this list, send
+ email to: questions-digest-request@postgreSQL.org with a BODY of:
+
+
+ subscribe
+ end
+
+ Digests are sent out to members of this list whenever the main list
+ has received around 30k of messages.
+
+ There is a bugs mailing list available. To subscribe to this list,
+ send email to bugs-request@postgreSQL.org with a BODY of:
+
+ There is also a developers discussion mailing list available. To
+ subscribe to this list, send email to hackers-request@postgreSQL.org
+ with a BODY of:
+
+
+ subscribe
+ end
+
+ Additional information about PostgreSQL can be found via the
+ PostgreSQL WWW home page at:
+
+ http://postgreSQL.org
+
+ 1.6) Latest release of PostgreSQL
+
+ The latest release of PostgreSQL is version 6.1.1, which will be
+ released in July, 1997. For information about what is new in 6.1.1,
+ see our TODO list on our WWW page.
+
+ We expect a 7.0 release in several months that will remove time-travel
+ and reduce by 50% the size of on-disk system columns maintained for
+ each row in a table. This release will also require a dump and
+ restore.
+
+ 1.7) Is there a commercial version of PostgreSQL?
+
+ Illustra Information Technology (a wholly owned subsidiary of Informix
+ Software, Inc.) sells an object-relational DBMS called Illustra that
+ was originally based on postgres. Illustra has cosmetic similarities
+ to PostgreSQL but has more features, is more robust, performs better,
+ and offers real documentation and support. On the flip side, it costs
+ money. For more information, contact sales@illustra.com
+
+ 1.8) What documentation is available for PostgreSQL?
+
+ A user manual, manual pages, and some small test examples are included
+ in the distribution. The sql and built-in manual pages are
+ particularly important.
+
+ The www page contains pointers to an implementation guide and five
+ papers written about postgres design concepts and features.
+
+ 1.9) What version of SQL does PostgreSQL use?
+
+ PostgreSQL supports a subset of SQL-92. It has most of the important
+ constructs but lacks some of the functionality. The most visible
+ differences are:
+ * no support for nested subqueries
+ * no HAVING clause under a GROUP BY
+
+ On the other hand, you get to create user-defined types, functions,
+ inheritance etc. If you're willing to help with PostgreSQL coding,
+ eventually we can also add the missing features listed above.
+
+ 1.10) Does PostgreSQL work with databases from earlier versions of postgres?
+
+ PostgreSQL v1.09 is compatible with databases created with v1.01.
+ Those upgrading from 1.0 should read the directions in the
+ MIGRATION_1.0_TO_1.02 directory.
+
+ Upgrading to 6.0 requires a dump and restore from previous releases.
+
+ Upgrading to 6.1 requires a dump and restore from previous releases.
+
+ Upgrading from 6.1 to 6.1.1 requires a compile of the new release,
+ recompile of all your custom applications to use the new libpq, and
+ then an install while the postmaster is temporarily stopped.
+
+ Those ugrading from versions earlier than 1.09 must upgrade to 1.09
+ first without a dump/reload, then dump the data from 1.09, and then
+ load it into 6.1.1.
+
+ 1.11) How many people use PostgreSQL?
+
+ Since we don't have any licensing or registration scheme, it's
+ impossible to tell. We do know hundreds copies of PostgreSQL v1.* have
+ been downloaded, and that there many hundreds of subscribers to the
+ mailing lists.
+
+ _________________________________________________________________
+
+Section 2: Installation Questions
+
+ 2.1) initdb doesn't run
+
+ * check to see that you have the proper paths set
+ * check that the 'postgres' user owns all the right files
+ * ensure that there are files in $PGDATA/files, and that they are
+ non-empty. If they aren't, then "gmake install" failed for some
+ reason
+
+ 2.2) when I start up the postmaster, I get "FindBackend: could not find a
+ backend to execute..." "postmaster: could not find backend to execute..."
+
+ You probably do not have the right path set up. The 'postgres'
+ executable needs to be in your path.
+
+ 2.3) The system seems to be confused about commas, decimal points, and date
+ formats.
+
+ Check your locale configuration. PostgreSQL uses the locale settings
+ of the user that ran the postmaster process. Set those accordingly for
+ your operating environment.
+
+ 2.4) How do I install PostgreSQL somewhere other than /usr/local/pgsql?
+
+ You need to edit Makefile.global and change POSTGRESDIR accordingly,
+ or create a Makefile.custom and define POSTGRESDIR there.
+
+ 2.5) When I run postmaster, I get a Bad System Call core dumped message.
+
+ It could be a variety of problems, but first check to see that you
+ have system V extensions installed on your kernel. PostgreSQL requires
+ kernel support for shared memory.
+
+ 2.6) When I try to start the postmaster, I get IpcMemoryCreate errors.
+
+ You either do not have shared memory configured properly in kernel or
+ you need to enlarge the shared memory available in the kernel. The
+ exact amount you need depends on your architecture and how many
+ buffers you configure postmaster to run with. For most systems, with
+ default buffer sizes, you need a minimum of ~760K.
+
+ 2.7) I have changed a source file, but a recompile does not see the change?
+
+ The Makefiles do not have the proper dependencies for include files.
+ You have to do a 'make clean' and then another 'make'.
+
+ _________________________________________________________________
+
+Section 3: PostgreSQL Features
+
+ 3.1) How do I specify a KEY or other constraints on a column?
+
+ Column constraints are not supported in PostgreSQL. As a consequence,
+ the system does not check for duplicates.
+
+ Under 6.0, create a unique index on the column. Attempts to create
+ duplicate of that column will report an error.
+
+ 3.2) Does PostgreSQL support nested subqueries?
+
+ Subqueries are not implemented, but they can be simulated using sql
+ functions.
+
+ 3.3) How do I define a unique indices?
+
+ PostgreSQL 6.0 supports unique indices.
+
+ 3.4) I've having a lot of problems using rules.
+
+ Currently, the rule system in PostgreSQL is mostly broken. It works
+ enough to support the view mechanism, but that's about it. Use
+ PostgreSQL rules at your own peril.
+
+ 3.5) I can't seem to write into the middle of large objects reliably.
+
+ The Inversion large object system in PostgreSQL is also mostly broken.
+ It works well enough for storing large wads of data and reading them
+ back out, but the implementation has some underlying problems. Use
+ PostgreSQL large objects at your own peril.
+
+ 3.6) Does PostgreSQL have a graphical user interface? A report generator? A
+ embedded query language interface?
+
+ No. No. No. Not in the official distribution at least. Some users have
+ reported some success at using 'pgbrowse' and 'onyx' as frontends to
+ PostgreSQL. Several contributions are working on tk based frontend
+ tools. Ask on the mailing list.
+
+ 3.7) How can I write client applications to PostgreSQL?
+
+ PostgreSQL supports a C-callable library interface called libpq as
+ well as a Tcl-based library interface called libtcl.
+
+ Others have contributed a perl interface and a WWW gateway to
+ PostgreSQL. See the PostgreSQL home pages for more details.
+
+ 3.8) How do I prevent other hosts from accessing my PostgreSQL backend?
+
+ Use host-based authentication by modifying the file $PGDATA/pg_hba
+ accordingly.
+
+ 3.9) How do I set up a pg_group?
+
+ Currently, there is no easy interface to set up user groups. You have
+ to explicitly insert/update the pg_group table. For example:
+
+
+ jolly=> insert into pg_group (groname, grosysid, grolist)
+ jolly=> values ('posthackers', '1234', '{5443, 8261}');
+ INSERT 548224
+ jolly=> grant insert on foo to group posthackers;
+ CHANGE
+ jolly=>
+
+ The fields in pg_group are:
+ * groname: the group name. This a char16 and should be purely
+ alphanumeric. Do not include underscores or other punctuation.
+ * grosysid: the group id. This is an int4. This should be unique for
+ each group.
+ * grolist: the list of pg_user id's that belong in the group. This
+ is an int4[].
+
+ 3.10) What is the exact difference between binary cursors and normal cursors?
+
+ Normal cursors return data back in ASCII format. Since data is stored
+ natively in binary format, the system must do a conversion to produce
+ the ASCII format. In addition, ASCII formats are often large in size
+ than binary format. Once the attributes come back in ASCII, often the
+ client application then has to convert it to a binary format to
+ manipulate it anyway.
+
+ Binary cursors give you back the data in the native binary
+ representation. Thus, binary cursors will tend to be a little faster
+ since there's less overhead of conversion.
+
+ However, ASCII is architectural neutral whereas binary representation
+ can differ between different machine architecture. Thus, if your
+ client machine uses a different representation than you server
+ machine, getting back attributes in binary format is probably not what
+ you want. Also, if your main purpose is displaying the data in ASCII,
+ then getting it back in ASCII will save you some effort on the client
+ side.
+
+ 3.11) Why doesn't the != operator work?
+
+ SQL specifies <> as the inequality operator, and that is what we have
+ defined for the built-in types.
+
+ In 6.0, != is equivalent to <>.
+
+ 3.12) What is a R-tree index and what is it used for?
+
+ An r-tree index is used for indexing spatial data. A hash index can't
+ handle range searches. A B-tree index only handles range searches in a
+ single dimension. R-tree's can handle multi-dimensional data. For
+ example, if a R-tree index can be built on an attribute of type
+ 'point', the system can more efficient answer queries like select all
+ points within a bounding rectangle.
+
+ The canonical paper that describes the original R-Tree design is:
+
+ Guttman, A. "R-Trees: A Dynamic Index Structure for Spatial
+ Searching." Proc of the 1984 ACM SIGMOD Int'l Conf on Mgmt of Data,
+ 45-57.
+
+ You can also find this paper in Stonebraker's "Readings in Database
+ Systems"
+
+ 3.13) What is the maximum size for a tuple?
+
+ Tuples are limited to 8K bytes. Taking into account system attributes
+ and other overhead, one should stay well shy of 8,000 bytes to be on
+ the safe side. To use attributes larger than 8K, try using the large
+ objects interface.
+
+ Tuples do not cross 8k boundaries so a 5k tuple will require 8k of
+ storage.
+
+ 3.14) I defined indices but my queries don't seem to make use of them. Why?
+
+ PostgreSQL does not automatically maintain statistics. One has to make
+ an explicit 'vacuum' call to update the statistics. After statistics
+ are updated, the optimizer has a better shot at using indices. Note
+ that the optimizer is limited and does not use indices in some
+ circumstances (such as OR clauses).
+
+ If the system still does not see the index, it is probably because you
+ have created an index on a field with the improper *_ops type. For
+ example, you have created a CHAR(4) field, but have specified a
+ char_ops index type_class.
+
+ See the create_index manual page for information on what type classes
+ are available. It must match the field type.
+
+ Postgres does not warn the user when the improper index is created.
+
+ Indexes not used for ORDER BY operations.
+
+ 3.15) Are there ODBC drivers for PostgreSQL?
+
+ There are two ODBC drivers available, PostODBC and OpenLink ODBC.
+
+ For all people being interested in PostODBC, there are now two mailing
+ lists devoted to the discussion of PostODBC. The mailing lists are:
+ * postodbc-users@listserv.direct. net
+ * postodbc-developers@listse rv.direct.net
+
+ these lists are ordinary majordomo mailing lists. You can subscribe by
+ sending a mail to:
+ * majordomo@listserv.direct.net
+
+ OpenLink ODBC is currently in beta under Linux. You can get it from
+ http://www.openlinksw.com/postgres.html. It works with our standard
+ ODBC client software so you'll have Postgres ODBC available on every
+ client platform we support (Win, Mac, Unix, VMS).
+
+ We will probably be selling this product to people who need
+ commercial-quality support, but a freeware version will always be
+ available. Questions to postgres95@openlink.co.uk.
+
+ 3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)?
+
+ Builtin R-Trees can handle polygons and boxes. In theory, R-trees can
+ be extended to handle higher number of dimensions. In practice,
+ extending R-trees require a bit of work and we don't currently have
+ any documentation on how to do it.
+
+ 3.17) How do I do regular expression searches? case-insensitive regexp
+ searching?
+
+ PostgreSQL supports the SQL LIKE syntax as well as more general
+ regular expression searching with the ~ operator. The !~ is the
+ negated regexp operator. ~* and !~* are the case-insensitive regular
+ expression operators.
+
+ 3.18) I can't access the database as the 'root' user.
+
+ You should not create database users with user id 0(root). They will
+ be unable to access the database. This is a security precaution
+ because of the ability of any user to dynamically link object modules
+ into the database engine.
+
+ 3.19) I experienced a server crash during a vacuum. How do I remove the lock
+ file?
+
+ If the server crashes during a vacuum command, chances are it will
+ leave a lock file hanging around. Attempts to re-run the vacuum
+ command result in
+
+
+ WARN:can't create lock file -- another vacuum cleaner running?
+
+ If you are sure that no vacuum is actually running, you can remove the
+ file called "pg_vlock" in your database directory (which is
+ $PGDATA/base/<dbName>)
+
+ 3.20) What is the difference between the various character types?
+
Type Internal Name Notes
--------------------------------------------------
CHAR char 1 character }
VARCHAR(#) varchar size specifies maximum length, no padding
TEXT text length limited only by maximum tuple length
BYTEA bytea variable-length array of bytes
-</PRE>
-<P>
-Remember, you need to use the internal name when creating indexes on
-these fields or when doing other internal operations.
-<P>
-The last four types above are "varlena" types (i.e. the first four bytes
-is the length, followed by the data). CHAR(#) and VARCHAR(#) allocate
-the maximum number of bytes no matter how much data is stored in the
-field. TEXT and BYTEA are the only character types that have variable
-length on the disk.
-<P>
-<H3><a name="3.21">3.21</a>) In a query, how do I detect if a field is NULL?</H3>
-<P>
-PostgreSQL has two builtin keywords, "isnull" and "notnull" (note no
-spaces). Version 1.05 and later and 6.* understand IS NULL and IS NOT
-NULL.
-<P>
-<H3><a name="3.22">3.22</a>) How do I see how the query optimizer is
-evaluating my query?</H3>
-<P>
-Place the word 'EXPLAIN' at the beginning of the query, for example:
-<PRE>
-<CODE>
- EXPLAIN SELECT * FROM table1 WHERE age = 23;
-</CODE>
-</PRE>
-<P>
-<H3><a name="3.23">3.23</a>) How do I create a serial field?</H3>
-<P>
-Postgres does not allow the user to specifiy a user column as type
-SERIAL. Instead, you can use each row's oid field as a unique value.
-However, if you need to dump and reload the database, you need to be
-using postgres version 1.07 or later or 6.* with pgdump's -o option or
-COPY's WITH OIDS option to preserver the oids.
-<P>
-Another valid way of doing this is to create a function:
-<PRE>
-<CODE>
- create table my_oids (f1 int4);
- insert into my_oids values (1);
- create function new_oid () returns int4 as
- 'update my_oids set f1 = f1 + 1; select f1 from my_oids; '
- language 'sql';
-</CODE>
-</PRE>
-<P>
-then:
-<PRE>
-<CODE>
- create table my_stuff (my_key int4, value text);
- insert into my_stuff values (new_oid(), 'hello');
-</CODE>
-</PRE>
-<P>
-However, keep in mind there is a race condition here where one server
-could do the update, then another one do an update, and they both could
-select the same new id. This statement should be performed within a
-transaction.
-<P>
-Sequences are implemented in 6.1
-<P>
-<H3><a name="3.24">3.24</a>) How do I create a multi-column index?</H3>
-<P>
-In 6.0, you can not directly create a multi-column index using create
-index. You need to define a function which acts on the multiple columns,
-then use create index with that function.
-<P>
-In 6.1, this feature is available.
-<P>
-<H3><a name="3.25">3.25</a>) What are the temp_XXX files in my database
-directory?</H3>
-<P>
-They are temp_ files generated by the query executor. For example, if a
-sort needs to be done to satisfy an ORDER BY, some temp files are
-generated as a result of the sort.
-<P>
-If you have no transactions or sorts running at the time, it is safe to
-delete the temp_ files.
-<P>
-<H3><a name="3.26">3.26</a>) Why are my table files not getting any
-smaller after a delete?</H3>
-<P>
-If you run vacuum in pre-6.0, unused rows will be marked for reuse, but
-the file blocks are not released.
-<P>
-In 6.0, vacuum properly shrinks tables.
-<P>
-<H3><a name="3.27">3.27</a>) Why can't I connect to my database from
-another machine?</H3>
-<P>
-The default configuration allows only connections from tcp/ip host
-localhost. You need to add a host entry to the file pgsql/data/pg_hba.
-<P>
-<H3><a name="3.28">3.28</a>) I get the error 'default index class
-unsupported' when creating an index. How do I do it?</H3>
-<P>
-You probably used:
-<PRE>
-<CODE>
- create index idx1 on person using btree (name);
-</CODE>
-</PRE>
-<P>
-PostgreSQL indexes are extensible, and therefore in pre-6.0, you must
-specify a class_type when creating an index. Read the manual page for
-create index (called create_index).
-<P>
-Version 6.0, if you do not specify a class_type, it defaults to the
-proper type for the column.
-<P>
-<H3><a name="3.29">3.29</a>) Why does creating an index crash the
-backend server?</H3>
-<P>
-You have probably defined an incorrect *_ops type class for the field
-you are indexing.
-<P>
-<H3><a name="3.30">3.30</a>) How do I find out what indexes or
-operations are defined in the database?</H3>
-<P>
-Run the file pgsql/src/tutorial/syscat.source. It illustrates many of
-the 'select's needed to get information out of the database system
-tables.
-<P>
-<H3><a name="3.31">3.31</a>) Why do statements require an extra character at
-the end? Why does 'createuser' return 'unexpected last match in input()'?
-Why does pg_dump fail?</H3>
-<P>
-You have compile postgres with flex version 2.5.3. There is bug in this
-version of flex. Use flex version 2.5.2 or flex 2.5.4 instead. There
-is a doc/README.flex file which will properly patch the flex 2.5.3
-source code.
-<P>
-<H3><a name="3.32">3.32</a>) All my servers crash under concurrent table
-access. Why?</H3>
-<P>
-This problem can be caused by a kernel that is not configured to support
-semaphores.
-<P>
-<H3><a name="3.33">3.33</a>) What tools are available for hooking
-postgres to Web pages?</H3>
-<P>
-For web integration, PHP/FI is an excellent interface. The URL for that
-is <a href="http://www.vex.net/php/">http://www.vex.net/php/</a>
-<P>
-PHP is great for simple stuff, but for more complex stuff, some still
-use the perl interface and CGI.pm.
-<P>
-An example of using WWW with C to talk to Postgres is can be tried at:
-<UL>
-<LI>
- <a href="http://postgreSQL.org/%7Emlc">http://postgreSQL.org/~mlc</a>
-</UL>
-<P>
-An WWW gatway based on WDB using perl can be downloaded from:
-<UL>
-<LI>
- <a
-href="http://www.eol.ists.ca/~dunlop/wdb-p95">http://www.eol.ists.ca/~dunlop/wdb
--p95</a>
-</UL>
-<H3><a name="3.34">3.34</a>) What is the time-warp feature and how does
-it relate to vacuum?</H3>
-<P>
-PostgreSQL handles data changes differently than most database systems.
-When a row is changed in a table, the original row is marked with the
-time it was changed, and a new row is created with the current data. By
-default, only current rows are used in a table. If you specify a
-date/time after the table name in a FROM clause, you can access the data
-that was current at that time, i.e.
-<PRE>
-<CODE>
- SELECT *
- FROM employees ['July 24, 1996 09:00:00']
-</CODE>
-</PRE>
-<P>
-displays employee rows in the table at the specified time. You can
-specify intervals like [date,date], [date,], [,date], or [,]. This last
-option accesses all rows that ever existed.
-<P>
-INSERTed rows get a timestamp too, so rows that were not in the table at
-the desired time will not appear.
-<P>
-Vacuum removes rows that are no longer current. This time-warp feature
-is used by the engine for rollback and crash recovery. Expiration times
-can be set with purge.
-<P>
-In 6.0, once a table is vacuumed, the creation time of a row may be
-incorrect, causing time-traval to fail.
-<P>
-The time-travel feature will be removed in 7.0.
-<P>
-<H3><a name="3.35">3.35</a>) How do I tune the database engine for
-better performance?</H3>
-<P>
-There are two things that can be done. You can use Openlink's option to
-disable fsync() by starting the postmaster with a '-o -F' option. This
-will prevent fsync()'s from flushing to disk after every transaction.
-<P>
-You can also use the postmaster -B option to increase the number of
-shared memory buffers shared among the backend processes. If you make
-this parameter too high, the process will not start or crash
-unexpectedly. Each buffer is 8K and the defualt is 64 buffers.
-<P>
-<H3><a name="3.36">3.36</a>) What debugging features are available in
-PostgreSQL?</H3>
-<P>
-PostgreSQL has several features that report status information that can
-be valuable for debugging purposes.
-<P>
-First, by compiling with DEBUG defined, many assert()'s monitor the
-progress of the backend and halt the program when something unexpected
-occurs.
-<P>
-Both postmaster and postgres have several debug options available.
-First, whenever you start the postmaster, make sure you send the
-standard output and error to a log file, like:
-<PRE>
-<KBD>
- cd /usr/local/pgsql
- ./bin/postmaster >server.log 2>&1 &
-</KBD>
-</PRE>
-<P>
-This will put a server.log file in the top-level PostgreSQL directory.
-This file can contain useful information about problems or errors
-encountered by the server. Postmaster has a -d option that allows even
-more detailed information to be reported. The -d option takes a number
-1-3 that specifies the debug level. The query plans in a verbose debug
-file can be formatted using the 'indent' program. (You may need to
-remove the '====' lines in 1.* releases.) Be warned that a debug level
-greater than one generates large log files in 1.* releases.
-<P>
-You can actuall run the postgres backend from the command line, and type
-your SQL statement directly. This is recommended ONLY for debugging
-purposes. Note that a newline terminates the query, not a semicolon. If
-you have compiled with debugging symbols, you can perhaps use a debugger
-to see what is happening. Because the backend was not started from the
-postmaster, it is not running in an identical environment and
-locking/backend interaction problems may not be duplicated. Some
-operating system can attach to a running backend directly to diagnose
-problems.
-<P>
-The postgres program has a -s, -A, -t options that can be very usefull
-for debugging and performance measurements.
-<P>
-The EXPLAIN command (see this FAQ) allows you to see how PostgreSQL is
-iterpreting your query.
-<P>
-<H3><a name="3.37">3.37</a>) What is an oid? What is a tid?</H3>
-<P>
-Oids are Postgres's answer to unique row ids or serial columns. Every
-row that is created in Postgres gets a unique oid. All oids generated
-by initdb are less than 16384 (from backend/access/transam.h). All
-post-initdb (user-created) oids are equal or greater that this. All
-these oids are unique not only within a table, or database, but unique
-within the entire postgres installation.
-<P>
-Postgres uses oids in its internal system tables to link rows in
-separate tables. These oids can be used to identify specific user rows
-and used in joins. It is recommended you use column type oid to store
-oid values. See the sql(l) manual page to see the other internal
-columns.
-<P>
-Tids are used to indentify specific physical rows with block and offset
-values. Tids change after rows are modified or reloaded. They are used
-by index entries to point to physical rows. They can not be accessed
-through sql.
-<P>
-<H3><a name="3.38">3.38</a>) What is the meaning of some of the terms
-used in Postgres?</H3>
-<P>
-Some of the source code and older documentation use terms that have more
-common usage. Here are some:
-<UL>
-<LI> row, record, tuple
-<LI> attribute, field, column
-<LI> table, class
-<LI> retrieve, select
-<LI> replace, update
-<LI> append, insert
-<LI> oid, serial value
-<LI> portal, cursor
-<LI> range variable, table name, table alias
-</UL>
-<P>
-Please let me know if you think of any more.
-<P>
-<H3><a name="3.39">3.39</a>) What is Genetic Query Optimization?</H3>
-<P>
-The GEQO module in PostgreSQL is intended to solve the query
-optimization problem of joining many tables by means of a Genetic
-Algorithm (GA). It allows the handling of large join queries through
-non-exhaustive search.
-<P>
-For further information see README.GEQO <utesch@aut.tu-freiberg.de>.
-<P>
-<H3><a name="3.40">3.40</a>) I am running Solaris and my dates
-display wrong. Why?</H3>
-<P>
-There was a bug in 6.0 that caused this problem under Solaris with -O2
-optimization.
-Upgrade to 6.1.
-<P>
-<H3><a name="3.41">3.41</a>) How do I enable more than 32 concurrent
-backends?</H3>
-<P>
-Edit include/storage/sinvaladt.h, and change the value of MaxBackendId.
-In the future, we plan to make this a configurable prameter.
-<P>
-<HR>
-<H2> Section 4: Extending PostgreSQL
-</H2>
-<P>
-<H3><a name="4.1">4.1</a>) I wrote a user-defined function and when I run it
-in psql, it dumps core.</H3>
-<P>
-The problem could be a number of things. Try testing your user-defined
-function in a stand alone test program first. Also, make sure you are
-not sending elog NOTICES when the front-end is expecting data, such as
-during a type_in() or type_out() functions
-<P>
-<H3><a name="4.2">4.2</a>) I get messages of the type
- NOTICE:PortalHeapMemoryFree: 0x402251d0 not in alloc set!</H3>
-<P>
-You are pfree'ing something that was not palloc'ed. When writing
-user-defined functions, do not include the file "libpq-fe.h". Doing so
-will cause your palloc to be a malloc instead of a free. Then, when the
-backend pfrees the storage, you get the notice message.
-<P>
-<H3><a name="4.3">4.3</a>) I've written some nifty new types and functions for
-PostgreSQL.</H3>
-<P>
-Please share them with other PostgreSQL users. Send your extensions to
-mailing list, and they will eventually end up in the contrib/
-subdirectory.
-<P>
-<H3><a name="4.4">4.4</a>) How do I write a C function to return a tuple?</H3>
-<P>
-This requires extreme wizardry, so extreme that the authors have not
-ever tried it, though in principle it can be done. The short answer is
-... you can't. This capability is forthcoming in the future.
-<P>
-<HR>
-<H2> Section 5: Bugs
-</H2>
-<P>
-<H3><a name="5.1">5.1</a>) How do I make a bug report?</H3>
-<P>
-Check the current FAQ at <a
-href="http://postgreSQL.org">http://postgreSQL.org</a>
-<P>
-Also check out our ftp site <a
-href="ftp://ftp.postgreSQL.org/pub">ftp://ftp.postgreSQL.org/pub</a> to
-see if there is a more recent PostgreSQL version.
-<P>
-You can also fill out the "bug-template" file and send it to:
-<UL>
-<LI> <a href="mailto:bugs@postgreSQL.org">bugs@postgreSQL.org</a>
-</UL>
-<P>
-This is the address of the developers mailing list.
-</BODY>
-</HTML>
+ Remember, you need to use the internal name when creating indexes on
+ these fields or when doing other internal operations.
+
+ The last four types above are "varlena" types (i.e. the first four
+ bytes is the length, followed by the data). CHAR(#) and VARCHAR(#)
+ allocate the maximum number of bytes no matter how much data is stored
+ in the field. TEXT and BYTEA are the only character types that have
+ variable length on the disk.
+
+ 3.21) In a query, how do I detect if a field is NULL?
+
+ PostgreSQL has two builtin keywords, "isnull" and "notnull" (note no
+ spaces). Version 1.05 and later and 6.* understand IS NULL and IS NOT
+ NULL.
+
+ 3.22) How do I see how the query optimizer is evaluating my query?
+
+ Place the word 'EXPLAIN' at the beginning of the query, for example:
+
+ EXPLAIN SELECT * FROM table1 WHERE age = 23;
+
+ 3.23) How do I create a serial field?
+
+ Postgres does not allow the user to specifiy a user column as type
+ SERIAL. Instead, you can use each row's oid field as a unique value.
+ However, if you need to dump and reload the database, you need to be
+ using postgres version 1.07 or later or 6.* with pgdump's -o option or
+ COPY's WITH OIDS option to preserver the oids.
+
+ Another valid way of doing this is to create a function:
+
+ create table my_oids (f1 int4);
+ insert into my_oids values (1);
+ create function new_oid () returns int4 as
+ 'update my_oids set f1 = f1 + 1; select f1 from my_oids; '
+ language 'sql';
+
+ then:
+
+ create table my_stuff (my_key int4, value text);
+ insert into my_stuff values (new_oid(), 'hello');
+
+ However, keep in mind there is a race condition here where one server
+ could do the update, then another one do an update, and they both
+ could select the same new id. This statement should be performed
+ within a transaction.
+
+ Sequences were implemented in 6.1
+
+ 3.24) How do I create a multi-column index?
+
+ In 6.0, you can not directly create a multi-column index using create
+ index. You need to define a function which acts on the multiple
+ columns, then use create index with that function.
+
+ In 6.1, this feature is available.
+
+ 3.25) What are the temp_XXX files in my database directory?
+
+ They are temp_ files generated by the query executor. For example, if
+ a sort needs to be done to satisfy an ORDER BY, some temp files are
+ generated as a result of the sort.
+
+ If you have no transactions or sorts running at the time, it is safe
+ to delete the temp_ files.
+
+ 3.26) Why are my table files not getting any smaller after a delete?
+
+ If you run vacuum in pre-6.0, unused rows will be marked for reuse,
+ but the file blocks are not released.
+
+ In 6.0, vacuum properly shrinks tables.
+
+ 3.27) Why can't I connect to my database from another machine?
+
+ The default configuration allows only connections from tcp/ip host
+ localhost. You need to add a host entry to the file pgsql/data/pg_hba.
+
+ 3.28) I get the error 'default index class unsupported' when creating an
+ index. How do I do it?
+
+ You probably used:
+
+ create index idx1 on person using btree (name);
+
+ PostgreSQL indexes are extensible, and therefore in pre-6.0, you must
+ specify a class_type when creating an index. Read the manual page for
+ create index (called create_index).
+
+ Version 6.0, if you do not specify a class_type, it defaults to the
+ proper type for the column.
+
+ 3.29) Why does creating an index crash the backend server?
+
+ You have probably defined an incorrect *_ops type class for the field
+ you are indexing.
+
+ 3.30) How do I find out what indexes or operations are defined in the
+ database?
+
+ Run the file pgsql/src/tutorial/syscat.source. It illustrates many of
+ the 'select's needed to get information out of the database system
+ tables.
+
+ 3.31) Why do statements require an extra character at the end? Why does
+ 'createuser' return 'unexpected last match in input()'? Why does pg_dump
+ fail?
+
+ You have compile postgres with flex version 2.5.3. There is bug in
+ this version of flex. Use flex version 2.5.2 or flex 2.5.4 instead.
+ There is a doc/README.flex file which will properly patch the flex
+ 2.5.3 source code.
+
+ 3.32) All my servers crash under concurrent table access. Why?
+
+ This problem can be caused by a kernel that is not configured to
+ support semaphores.
+
+ 3.33) What tools are available for hooking postgres to Web pages?
+
+ For web integration, PHP/FI is an excellent interface. The URL for
+ that is http://www.vex.net/php/
+
+ PHP is great for simple stuff, but for more complex stuff, some still
+ use the perl interface and CGI.pm.
+
+ An example of using WWW with C to talk to Postgres is can be tried at:
+ * http://postgreSQL.org/~mlc
+
+ An WWW gatway based on WDB using perl can be downloaded from:
+ * http://www.eol.ists.ca/~dunlop/wdb -p95
+
+ 3.34) What is the time-warp feature and how does it relate to vacuum?
+
+ PostgreSQL handles data changes differently than most database
+ systems. When a row is changed in a table, the original row is marked
+ with the time it was changed, and a new row is created with the
+ current data. By default, only current rows are used in a table. If
+ you specify a date/time after the table name in a FROM clause, you can
+ access the data that was current at that time, i.e.
+
+
+ SELECT *
+ FROM employees ['July 24, 1996 09:00:00']
+
+ displays employee rows in the table at the specified time. You can
+ specify intervals like [date,date], [date,], [,date], or [,]. This
+ last option accesses all rows that ever existed.
+
+ INSERTed rows get a timestamp too, so rows that were not in the table
+ at the desired time will not appear.
+
+ Vacuum removes rows that are no longer current. This time-warp feature
+ is used by the engine for rollback and crash recovery. Expiration
+ times can be set with purge.
+
+ In 6.0, once a table is vacuumed, the creation time of a row may be
+ incorrect, causing time-traval to fail.
+
+ The time-travel feature will be removed in 7.0.
+
+ 3.35) How do I tune the database engine for better performance?
+
+ There are two things that can be done. You can use Openlink's option
+ to disable fsync() by starting the postmaster with a '-o -F' option.
+ This will prevent fsync()'s from flushing to disk after every
+ transaction.
+
+ You can also use the postmaster -B option to increase the number of
+ shared memory buffers shared among the backend processes. If you make
+ this parameter too high, the process will not start or crash
+ unexpectedly. Each buffer is 8K and the defualt is 64 buffers.
+
+ 3.36) What debugging features are available in PostgreSQL?
+
+ PostgreSQL has several features that report status information that
+ can be valuable for debugging purposes.
+
+ First, by compiling with DEBUG defined, many assert()'s monitor the
+ progress of the backend and halt the program when something unexpected
+ occurs.
+
+ Both postmaster and postgres have several debug options available.
+ First, whenever you start the postmaster, make sure you send the
+ standard output and error to a log file, like:
+
+
+ cd /usr/local/pgsql
+ ./bin/postmaster >server.log 2>&1 &
+
+ This will put a server.log file in the top-level PostgreSQL directory.
+ This file can contain useful information about problems or errors
+ encountered by the server. Postmaster has a -d option that allows even
+ more detailed information to be reported. The -d option takes a number
+ 1-3 that specifies the debug level. The query plans in a verbose debug
+ file can be formatted using the 'indent' program. (You may need to
+ remove the '====' lines in 1.* releases.) Be warned that a debug level
+ greater than one generates large log files in 1.* releases.
+
+ You can actuall run the postgres backend from the command line, and
+ type your SQL statement directly. This is recommended ONLY for
+ debugging purposes. Note that a newline terminates the query, not a
+ semicolon. If you have compiled with debugging symbols, you can
+ perhaps use a debugger to see what is happening. Because the backend
+ was not started from the postmaster, it is not running in an identical
+ environment and locking/backend interaction problems may not be
+ duplicated. Some operating system can attach to a running backend
+ directly to diagnose problems.
+
+ The postgres program has a -s, -A, -t options that can be very usefull
+ for debugging and performance measurements.
+
+ The EXPLAIN command (see this FAQ) allows you to see how PostgreSQL is
+ iterpreting your query.
+
+ 3.37) What is an oid? What is a tid?
+
+ Oids are Postgres's answer to unique row ids or serial columns. Every
+ row that is created in Postgres gets a unique oid. All oids generated
+ by initdb are less than 16384 (from backend/access/transam.h). All
+ post-initdb (user-created) oids are equal or greater that this. All
+ these oids are unique not only within a table, or database, but unique
+ within the entire postgres installation.
+
+ Postgres uses oids in its internal system tables to link rows in
+ separate tables. These oids can be used to identify specific user rows
+ and used in joins. It is recommended you use column type oid to store
+ oid values. See the sql(l) manual page to see the other internal
+ columns.
+
+ Tids are used to indentify specific physical rows with block and
+ offset values. Tids change after rows are modified or reloaded. They
+ are used by index entries to point to physical rows. They can not be
+ accessed through sql.
+
+ 3.38) What is the meaning of some of the terms used in Postgres?
+
+ Some of the source code and older documentation use terms that have
+ more common usage. Here are some:
+ * row, record, tuple
+ * attribute, field, column
+ * table, class
+ * retrieve, select
+ * replace, update
+ * append, insert
+ * oid, serial value
+ * portal, cursor
+ * range variable, table name, table alias
+
+ Please let me know if you think of any more.
+
+ 3.39) What is Genetic Query Optimization?
+
+ The GEQO module in PostgreSQL is intended to solve the query
+ optimization problem of joining many tables by means of a Genetic
+ Algorithm (GA). It allows the handling of large join queries through
+ non-exhaustive search.
+
+ For further information see README.GEQO <utesch@aut.tu-freiberg.de>.
+
+ 3.40) I am running Solaris and my dates display wrong. Why?
+
+ There was a bug in 6.0 that caused this problem under Solaris with -O2
+ optimization. Upgrade to 6.1.1.
+
+ 3.41) How do I enable more than 32 concurrent backends?
+
+ Edit include/storage/sinvaladt.h, and change the value of
+ MaxBackendId. In the future, we plan to make this a configurable
+ prameter.
+
+ _________________________________________________________________
+
+Section 4: Extending PostgreSQL
+
+ 4.1) I wrote a user-defined function and when I run it in psql, it dumps
+ core.
+
+ The problem could be a number of things. Try testing your user-defined
+ function in a stand alone test program first. Also, make sure you are
+ not sending elog NOTICES when the front-end is expecting data, such as
+ during a type_in() or type_out() functions
+
+ 4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0 not
+ in alloc set!
+
+ You are pfree'ing something that was not palloc'ed. When writing
+ user-defined functions, do not include the file "libpq-fe.h". Doing so
+ will cause your palloc to be a malloc instead of a free. Then, when
+ the backend pfrees the storage, you get the notice message.
+
+ 4.3) I've written some nifty new types and functions for PostgreSQL.
+
+ Please share them with other PostgreSQL users. Send your extensions to
+ mailing list, and they will eventually end up in the contrib/
+ subdirectory.
+
+ 4.4) How do I write a C function to return a tuple?
+
+ This requires extreme wizardry, so extreme that the authors have not
+ ever tried it, though in principle it can be done. The short answer is
+ ... you can't. This capability is forthcoming in the future.
+
+ _________________________________________________________________
+
+Section 5: Bugs
+
+ 5.1) How do I make a bug report?
+
+ Check the current FAQ at http://postgreSQL.org
+
+ Also check out our ftp site ftp://ftp.postgreSQL.org/pub to see if
+ there is a more recent PostgreSQL version.
+
+ You can also fill out the "bug-template" file and send it to:
+ * bugs@postgreSQL.org
+
+ This is the address of the developers mailing list.
projects / thirdparty / postgresql.git / commitdiff
