Clarify the purpose of the nField argument passed to sqlite3VdbeSorterInit().

FossilOrigin-Name: c0c8cff17b7311bbc4fd081313a5552f927c3833

diff --git a/manifest b/manifest
index b476a4c7f2cec7a4641d23e7f3ef74b212398743..df788673d33df7aba644c9f9cfaac040e652e0ca 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Change\sthe\sname\sof\svdbeIncrInit2\sto\svdbePmaReaderIncrInit.\sAdd\sa\sheader\scomment\sto\sthe\ssame\sfunction.
-D 2014-04-16T17:41:22.128
+C Clarify\sthe\spurpose\sof\sthe\snField\sargument\spassed\sto\ssqlite3VdbeSorterInit().
+D 2014-04-16T19:04:23.830
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in ad0921c4b2780d01868cf69b419a4f102308d125
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -286,7 +286,7 @@ F src/vdbeapi.c 0ed6053f947edd0b30f64ce5aeb811872a3450a4
 F src/vdbeaux.c d8dc38965507a34b0e150c0d7fc82b02f8cf25ea
 F src/vdbeblob.c 15377abfb59251bccedd5a9c7d014a895f0c04aa
 F src/vdbemem.c 6fc77594c60f6155404f3f8d71bf36d1fdeb4447
-F src/vdbesort.c 70e42f93ebc6c4b08fff55f3f3bc6b25916cfeda
+F src/vdbesort.c fcd15eb438a3462f4dbeebf506ee9050947236bf
 F src/vdbetrace.c 6f52bc0c51e144b7efdcfb2a8f771167a8816767
 F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
 F src/wal.c 76e7fc6de229bea8b30bb2539110f03a494dc3a8
@@ -1164,7 +1164,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P 69026ec7dc3bd3e33bbe17c221a53cf1dd0f8945
-R ed75157562bc112af42ea8e3070ab11f
+P 6622d87675c1d7992b1e6d52ae7da1007a1568a4
+R dd88eb57ef2cb3488d23de10e0a80225
 U dan
-Z ff87db58800fcd075476469fa2fb9f2f
+Z 28b7dc83a03f9f7e8d724df0f79c29e1

diff --git a/manifest.uuid b/manifest.uuid
index 52fd8bbfbc0084a0682e891ac0ab00fc51db84da..8d63094336803c57b84240788522318d824a3b87 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-6622d87675c1d7992b1e6d52ae7da1007a1568a4
\ No newline at end of file
+c0c8cff17b7311bbc4fd081313a5552f927c3833
\ No newline at end of file

diff --git a/src/vdbesort.c b/src/vdbesort.c
index 348eb447fd149962f629031e17b40c9417e8e490..63f17e4e774e0201c514b82bb625e496d5814bbc 100644 (file)
--- a/src/vdbesort.c
+++ b/src/vdbesort.c
@@ -794,6 +794,22 @@ static int vdbeSorterDoCompare(
 
 /*
 ** Initialize the temporary index cursor just opened as a sorter cursor.
+**
+** Usually, the sorter module uses the value of (pCsr->pKeyInfo->nField)
+** to determine the number of fields that should be compared from the
+** records being sorted. However, if the value passed as argument nField
+** is non-zero and the sorter is able to guarantee a stable sort, nField
+** is used instead. This is used when sorting records for a CREATE INDEX
+** statement. In this case, keys are always delivered to the sorter in
+** order of the primary key, which happens to be make up the final part 
+** of the records being sorted. So if the sort is stable, there is never
+** any reason to compare PK fields and they can be ignored for a small
+** performance boost.
+**
+** The sorter can guarantee a stable sort when running in single-threaded
+** mode, but not in multi-threaded mode.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
 */
 int sqlite3VdbeSorterInit(
   sqlite3 *db,                    /* Database connection (for malloc()) */