From: drh Date: Wed, 9 Nov 2016 20:14:34 +0000 (+0000) Subject: Comment changes that attempt to better explain the behavior of the "seekResult" X-Git-Tag: version-3.16.0~126^2~6 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=eaf6ae29928eee11076fc6a0577e2630a6e56b4f;p=thirdparty%2Fsqlite.git Comment changes that attempt to better explain the behavior of the "seekResult" field on VdbeCursor objects and the seekResult parameter to sqlite3BtreeInsert() and the OPFLAG_USESEEKRESULT flag on insert opcodes. No changes to code. FossilOrigin-Name: 345b46be75bdf6f9fb7367a6164d89bae11995a6 --- diff --git a/manifest b/manifest index 47015a4f64..e5e5f23851 100644 --- a/manifest +++ b/manifest @@ -1,5 +1,5 @@ -C Fix\sa\ssimple\scomment\stypo.\s\sNo\schanges\sto\scode. -D 2016-11-09T16:03:36.041 +C Comment\schanges\sthat\sattempt\sto\sbetter\sexplain\sthe\sbehavior\sof\sthe\s"seekResult"\nfield\son\sVdbeCursor\sobjects\sand\sthe\sseekResult\sparameter\sto\nsqlite3BtreeInsert()\sand\sthe\sOPFLAG_USESEEKRESULT\sflag\son\sinsert\sopcodes.\nNo\schanges\sto\scode. +D 2016-11-09T20:14:34.342 F Makefile.in 6fd48ffcf7c2deea7499062d1f3747f986c19678 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434 F Makefile.msc e0217f2d35a0448abbe4b066132ae20136e8b408 @@ -330,7 +330,7 @@ F src/auth.c 930b376a9c56998557367e6f7f8aaeac82a2a792 F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b F src/bitvec.c 3ee4c8b2c94ed3a7377256e18199e6ff5cf33f63 F src/btmutex.c bc87dd3b062cc26edfe79918de2200ccb8d41e73 -F src/btree.c fa0e4f2656562f18a8aeab5faa5747fc2d6bc497 +F src/btree.c d1a3d691917cb7d67d50318aef990d8f30d172c7 F src/btree.h 630303068c82a359f6ddf202b205ae927721b090 F src/btreeInt.h c18b7d2a3494695133e4e60ee36061d37f45d9a5 F src/build.c 178f16698cbcb43402c343a9413fe22c99ffee21 @@ -454,9 +454,9 @@ F src/update.c 771335a33c958a186b66ef7e349f978d6bb2aac4 F src/utf.c 699001c79f28e48e9bcdf8a463da029ea660540c F src/util.c 3e2da6101888d073e79ecc6af5e0a2f70fa1e498 F src/vacuum.c 33c174b28886b2faf26e503b5a49a1c01a9b1c16 -F src/vdbe.c e6bf36b1df5ff32d222e8c96cacb2fb951be42a2 +F src/vdbe.c f1a8e5bf7747f2e731812804cb65d4d07d86862e F src/vdbe.h c044be7050ac6bf596eecc6ab159f5dbc020a3b7 -F src/vdbeInt.h d8a56a491b752dbb5f671963b8c861ec72ea875e +F src/vdbeInt.h 29b25318a0286c4b2599c0fbef6acf524398489a F src/vdbeapi.c 97129bec6b1553da50d8e73f523c278bda66d9f6 F src/vdbeaux.c 52d9b840859f260ce8418be9333dd77c902e1c74 F src/vdbeblob.c 3e82a797b60c3b9fed7b8de8c539ca7607874937 @@ -1530,7 +1530,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0 -P 42db7cd2c0b367f7dfe733bdaf006538937b812a -R 725472132a567caa1a975d92e1d85b3c +P 51d0aed8d63d0710e4aa8925ff18cf3c45dc9e42 +R eacb8afe762fb37c4ccfd0b85c6e6ad7 U drh -Z 171f352f5da597b47d092f93a00f48a7 +Z e647112eb568bcacd99f7ceac7bd6ee3 diff --git a/manifest.uuid b/manifest.uuid index 6bee48823a..f7958c7d13 100644 --- a/manifest.uuid +++ b/manifest.uuid @@ -1 +1 @@ -51d0aed8d63d0710e4aa8925ff18cf3c45dc9e42 \ No newline at end of file +345b46be75bdf6f9fb7367a6164d89bae11995a6 \ No newline at end of file diff --git a/src/btree.c b/src/btree.c index 541a581e5d..b92b6018b4 100644 --- a/src/btree.c +++ b/src/btree.c @@ -7940,17 +7940,19 @@ static int balance(BtCursor *pCur){ ** pX.pData,nData,nZero fields must be zero. ** ** If the seekResult parameter is non-zero, then a successful call to -** MovetoUnpacked() to seek cursor pCur to (pKey, nKey) has already -** been performed. seekResult is the search result returned (a negative -** number if pCur points at an entry that is smaller than (pKey, nKey), or -** a positive value if pCur points at an entry that is larger than -** (pKey, nKey)). -** -** If the seekResult parameter is non-zero, then the caller guarantees that -** cursor pCur is pointing at the existing copy of a row that is to be -** overwritten. If the seekResult parameter is 0, then cursor pCur may -** point to any entry or to no entry at all and so this function has to seek -** the cursor before the new key can be inserted. +** MovetoUnpacked() to seek cursor pCur to (pKey,nKey) has already +** been performed. In other words, if seekResult!=0 then the cursor +** is currently pointing to a cell that will be adjacent to the cell +** to be inserted. If seekResult<0 then pCur points to a cell that is +** smaller then (pKey,nKey). If seekResult>0 then pCur points to a cell +** that is larger than (pKey,nKey). +** +** If seekResult==0, that means pCur is pointing at some unknown location. +** In that case, this routine must seek the cursor to the correct insertion +** point for (pKey,nKey) before doing the insertion. For index btrees, +** if pX->nMem is non-zero, then pX->aMem contains pointers to the unpacked +** key values and pX->aMem can be used instead of pX->pKey to avoid having +** to decode the key. */ int sqlite3BtreeInsert( BtCursor *pCur, /* Insert data into the table of this cursor */ diff --git a/src/vdbe.c b/src/vdbe.c index e37bf0da14..740e52fc90 100644 --- a/src/vdbe.c +++ b/src/vdbe.c @@ -4322,15 +4322,10 @@ case OP_NewRowid: { /* out2 */ ** then rowid is stored for subsequent return by the ** sqlite3_last_insert_rowid() function (otherwise it is unmodified). ** -** If the OPFLAG_USESEEKRESULT flag of P5 is set and if the result of -** the last seek operation (OP_NotExists or OP_SeekRowid) was a success, -** then this -** operation will not attempt to find the appropriate row before doing -** the insert but will instead overwrite the row that the cursor is -** currently pointing to. Presumably, the prior OP_NotExists or -** OP_SeekRowid opcode -** has already positioned the cursor correctly. This is an optimization -** that boosts performance by avoiding redundant seeks. +** If the OPFLAG_USESEEKRESULT flag of P5 is set, the implementation might +** run faster by avoiding an unnecessary seek on cursor P1. However, +** the OPFLAG_USESEEKRESULT flag must only be set if there have been no prior +** seeks on the cursor or if the most recent seek used a key equal to P3. ** ** If the OPFLAG_ISUPDATE flag is set, then this opcode is part of an ** UPDATE operation. Otherwise (if the flag is clear) then this opcode @@ -5036,9 +5031,11 @@ next_tail: ** incremented by this instruction. If the OPFLAG_NCHANGE bit is clear, ** then the change counter is unchanged. ** -** If P5 has the OPFLAG_USESEEKRESULT bit set, then the cursor must have -** just done a seek to the spot where the new entry is to be inserted. -** This flag avoids doing an extra seek. +** If the OPFLAG_USESEEKRESULT flag of P5 is set, the implementation might +** run faster by avoiding an unnecessary seek on cursor P1. However, +** the OPFLAG_USESEEKRESULT flag must only be set if there have been no prior +** seeks on the cursor or if the most recent seek used a key equivalent +** to P2. ** ** This instruction only works for indices. The equivalent instruction ** for tables is OP_Insert. diff --git a/src/vdbeInt.h b/src/vdbeInt.h index 86445cef66..6e6ace207c 100644 --- a/src/vdbeInt.h +++ b/src/vdbeInt.h @@ -96,7 +96,10 @@ struct VdbeCursor { } uc; Btree *pBt; /* Separate file holding temporary table */ KeyInfo *pKeyInfo; /* Info about index keys needed by index cursors */ - int seekResult; /* Result of previous sqlite3BtreeMoveto() */ + int seekResult; /* Result of previous sqlite3BtreeMoveto() or 0 + ** if there have been no prior seeks on the cursor. */ + /* NB: seekResult does not distinguish between "no seeks have ever occurred + ** on this cursor" and "the most recent seek was an exact match". */ i64 seqCount; /* Sequence counter */ i64 movetoTarget; /* Argument to the deferred sqlite3BtreeMoveto() */ VdbeCursor *pAltCursor; /* Associated index cursor from which to read */