Improved comments on the FORDELETE hint. No logic changes.

FossilOrigin-Name: a3cec529f0238e4ca1196fec420f2de80d28db78

diff --git a/manifest b/manifest
index 7d2bd6536731ca03aaf3074655cd08082cc29884..d459ef1f26c6bef0ac81c19b89839f8819387550 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\s'rbu'\sto\sthe\sclean\stargets.
-D 2016-01-20T18:47:59.553
+C Improved\scomments\son\sthe\sFORDELETE\shint.\s\sNo\slogic\schanges.
+D 2016-01-21T15:55:37.704
 F Makefile.in 7be88f5b473891e3a8c07245ed60535fcda4f9ee
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc c5ead4aa22ff6f528c755b07ed1e31184ac5b3d2
@@ -289,7 +289,7 @@ F src/backup.c 2869a76c03eb393ee795416e2387005553df72bc
 F src/bitvec.c 1a78d450a17c5016710eec900bedfc5729bf9bdf
 F src/btmutex.c bc87dd3b062cc26edfe79918de2200ccb8d41e73
 F src/btree.c f224ae877fde69d1a9d430f502edaf8502752dbe
-F src/btree.h 68ef301795e00cdf1d3ab93abc44a43b7fe771e0
+F src/btree.h 526137361963e746949ab966a910c7f455ac6b04
 F src/btreeInt.h c18b7d2a3494695133e4e60ee36061d37f45d9a5
 F src/build.c 31af80bba31ac159967951ef58f3144cc7db9d70
 F src/callback.c 29ae4faba226c7ebb9aee93016b5ce8a8f071261
@@ -350,7 +350,7 @@ F src/shell.c dcd7a83645ef2a58ee9c6d0ea4714d877d7835c4
 F src/sqlite.h.in 214476a62012e578f42133a9a3b4f97a9aa421a3
 F src/sqlite3.rc 992c9f5fb8285ae285d6be28240a7e8d3a7f2bad
 F src/sqlite3ext.h dfbe62ffd95b99afe2140d8c35b180d11924072d
-F src/sqliteInt.h 8c1debffeeb1579bdc264d54c72c05892e23b7ee
+F src/sqliteInt.h 0403328581127bc8ad2f9cc7af2c3bb23d5316da
 F src/sqliteLimit.h 216557999cb45f2e3578ed53ebefe228d779cb46
 F src/status.c 70912d7be68e9e2dbc4010c93d344af61d4c59ba
 F src/table.c 51b46b2a62d1b3a959633d593b89bab5e2c9155e
@@ -424,7 +424,7 @@ F src/vxworks.h 974e7d9a98f602d6310d563e1dc4e08f9fc48e47
 F src/wal.c d21b99fd1458159d0b1ecdccc8ee6ada4fdc4c54
 F src/wal.h 2f7c831cf3b071fa548bf2d5cac640846a7ff19c
 F src/walker.c 0f142b5bd3ed2041fc52d773880748b212e63354
-F src/where.c bb69654f841ae7af0a20cc6fb8f0ac57901c31be
+F src/where.c af9bf5dcec1a0e52726c550924aa91d837166251
 F src/whereInt.h 78b6b4de94db84aecbdc07fe3e38f648eb391e9a
 F src/wherecode.c 8dee26eb181ea9daa8b1a4d96f34c0860aaf99bd
 F src/whereexpr.c 197a448b52073aee43eca3a2233fc113369eb2d4
@@ -1419,7 +1419,7 @@ F tool/vdbe_profile.tcl 246d0da094856d72d2c12efec03250d71639d19f
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 81e830e21f81b6428209afa0b8f42f2fd9bd7aab
-R 48465c96540143107ca11194f4f37f5c
-U mistachkin
-Z 6a809d8da8a8f3c2b9daa12aa587edb1
+P f60f025027ab3acdbc97701f81ff9c11c8463022
+R 58c662ebb54c7087fe70ba0b9b653627
+U drh
+Z 656e64b9ebb4ed29ac85ca9fad2e65b0

diff --git a/manifest.uuid b/manifest.uuid
index 849ae0e2a6bc48212ebbd673097db687ed1a1c36..80d0db3e83620ce1d7dda631012a8553a87310f9 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-f60f025027ab3acdbc97701f81ff9c11c8463022
\ No newline at end of file
+a3cec529f0238e4ca1196fec420f2de80d28db78
\ No newline at end of file

diff --git a/src/btree.h b/src/btree.h
index 2f398e7bbabe1fde0f7b924d0f1343a00b446a5b..37a9915edad909f28cafcf44583682bb09cd86af 100644 (file)
--- a/src/btree.h
+++ b/src/btree.h
@@ -199,14 +199,24 @@ int sqlite3BtreeNewDb(Btree *p);
 ** Flags passed as the third argument to sqlite3BtreeCursor().
 **
 ** For read-only cursors the wrFlag argument is always zero. For read-write
-** cursors it may be set to either (BTREE_WRCSR|BTREE_FORDELETE) or
-** (BTREE_WRCSR). If the BTREE_FORDELETE flag is set, then the cursor will
+** cursors it may be set to either (BTREE_WRCSR|BTREE_FORDELETE) or just
+** (BTREE_WRCSR). If the BTREE_FORDELETE bit is set, then the cursor will
 ** only be used by SQLite for the following:
 **
-**   * to seek to and delete specific entries, and/or
+**   * to seek to and then delete specific entries, and/or
 **
 **   * to read values that will be used to create keys that other
 **     BTREE_FORDELETE cursors will seek to and delete.
+**
+** The BTREE_FORDELETE flag is an optimization hint.  It is not used by
+** by this, the native b-tree engine of SQLite, but it is available to
+** alternative storage engines that might be substituted in place of this
+** b-tree system.  For alternative storage engines in which a delete of
+** the main table row automatically deletes corresponding index rows,
+** the FORDELETE flag hint allows those alternative storage engines to
+** skip a lot of work.  Namely:  FORDELETE cursors may treat all SEEK
+** and DELETE operations as no-ops, and any READ operation against a
+** FORDELETE cursor may return a null row: 0x01 0x00.
 */
 #define BTREE_WRCSR     0x00000004     /* read-write cursor */
 #define BTREE_FORDELETE 0x00000008     /* Cursor is for seek/delete only */

diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 8ab59b467968b65a15048e8bd2a2c152743b2234..b536b8ab280b25dc13c321e7ee1738601df233e1 100644 (file)
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2857,7 +2857,7 @@ struct AuthContext {
 #define OPFLAG_TYPEOFARG     0x80    /* OP_Column only used for typeof() */
 #define OPFLAG_BULKCSR       0x01    /* OP_Open** used to open bulk cursor */
 #define OPFLAG_SEEKEQ        0x02    /* OP_Open** cursor uses EQ seek only */
-#define OPFLAG_FORDELETE     0x08    /* OP_Open is opening for-delete csr */
+#define OPFLAG_FORDELETE     0x08    /* OP_Open should use BTREE_FORDELETE */
 #define OPFLAG_P2ISREG       0x10    /* P2 to OP_Open** is a register number */
 #define OPFLAG_PERMUTE       0x01    /* OP_Compare: use the permutation */
 

diff --git a/src/where.c b/src/where.c
index 2cb8334ffbfe3b8a0786eda6710e0abe98b6a988..8c8dfbb7b627f07086bf3eeb89bd8ecd3e4451ba 100644 (file)
--- a/src/where.c
+++ b/src/where.c
@@ -4014,7 +4014,7 @@ WhereInfo *sqlite3WhereBegin(
   int ii;                    /* Loop counter */
   sqlite3 *db;               /* Database connection */
   int rc;                    /* Return code */
-  u8 bFordelete = 0;
+  u8 bFordelete = 0;         /* OPFLAG_FORDELETE or zero, as appropriate */
 
   assert( (wctrlFlags & WHERE_ONEPASS_MULTIROW)==0 || (
         (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 
@@ -4259,16 +4259,15 @@ WhereInfo *sqlite3WhereBegin(
 
   /* If the caller is an UPDATE or DELETE statement that is requesting
   ** to use a one-pass algorithm, determine if this is appropriate.
-  ** The one-pass algorithm only works if the WHERE clause constrains
-  ** the statement to update or delete a single row.
   */
   assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
   if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 ){
     int wsFlags = pWInfo->a[0].pWLoop->wsFlags;
     int bOnerow = (wsFlags & WHERE_ONEROW)!=0;
-    if( bOnerow || ( (wctrlFlags & WHERE_ONEPASS_MULTIROW)
-       && 0==(wsFlags & WHERE_VIRTUALTABLE)
-    )){
+    if( bOnerow
+     || ((wctrlFlags & WHERE_ONEPASS_MULTIROW)!=0
+           && 0==(wsFlags & WHERE_VIRTUALTABLE))
+    ){
       pWInfo->eOnePass = bOnerow ? ONEPASS_SINGLE : ONEPASS_MULTI;
       if( HasRowid(pTabList->a[0].pTab) && (wsFlags & WHERE_IDX_ONLY) ){
         if( wctrlFlags & WHERE_ONEPASS_MULTIROW ){