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Avoid writing the sqlite_sequence table when it has not actually changed.

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FossilOrigin-Name: 3e3849a9d1a06673e6c713a42194f5da339fbf6533fa418c38f63d09bc045867
This commit is contained in:
drh
2018-03-16 18:46:30 +00:00
parent 9f2b04533e
commit c8abbc11cd
3 changed files with 32 additions and 21 deletions
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34
src/insert.c
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@@ -210,11 +210,12 @@ static int readsTable(Parse *p, int iDb, Table *pTab){
** first use of table pTab. On 2nd and subsequent uses, the original
** AutoincInfo structure is used.
**
** Three memory locations are allocated:
** Four consecutive registers are allocated:
**
** (1) Register to hold the name of the pTab table.
** (2) Register to hold the maximum ROWID of pTab.
** (3) Register to hold the rowid in sqlite_sequence of pTab
** (1) The name of the pTab table.
** (2) The maximum ROWID of pTab.
** (3) The rowid in sqlite_sequence of pTab
** (4) The original value of the max ROWID in pTab, or NULL if none
**
** The 2nd register is the one that is returned. That is all the
** insert routine needs to know about.
@@ -242,7 +243,7 @@ static int autoIncBegin(
pInfo->iDb = iDb;
pToplevel->nMem++; /* Register to hold name of table */
pInfo->regCtr = ++pToplevel->nMem; /* Max rowid register */
pToplevel->nMem++; /* Rowid in sqlite_sequence */
pToplevel->nMem +=2; /* Rowid in sqlite_sequence + orig max val */
}
memId = pInfo->regCtr;
}
@@ -270,15 +271,17 @@ void sqlite3AutoincrementBegin(Parse *pParse){
static const int iLn = VDBE_OFFSET_LINENO(2);
static const VdbeOpList autoInc[] = {
/* 0 */ {OP_Null, 0, 0, 0},
/* 1 */ {OP_Rewind, 0, 9, 0},
/* 1 */ {OP_Rewind, 0, 10, 0},
/* 2 */ {OP_Column, 0, 0, 0},
/* 3 */ {OP_Ne, 0, 7, 0},
/* 3 */ {OP_Ne, 0, 9, 0},
/* 4 */ {OP_Rowid, 0, 0, 0},
/* 5 */ {OP_Column, 0, 1, 0},
/* 6 */ {OP_Goto, 0, 9, 0},
/* 7 */ {OP_Next, 0, 2, 0},
/* 8 */ {OP_Integer, 0, 0, 0},
/* 9 */ {OP_Close, 0, 0, 0}
/* 6 */ {OP_AddImm, 0, 0, 0},
/* 7 */ {OP_Copy, 0, 0, 0},
/* 8 */ {OP_Goto, 0, 11, 0},
/* 9 */ {OP_Next, 0, 2, 0},
/* 10 */ {OP_Integer, 0, 0, 0},
/* 11 */ {OP_Close, 0, 0, 0}
};
VdbeOp *aOp;
pDb = &db->aDb[p->iDb];
@@ -289,14 +292,17 @@ void sqlite3AutoincrementBegin(Parse *pParse){
aOp = sqlite3VdbeAddOpList(v, ArraySize(autoInc), autoInc, iLn);
if( aOp==0 ) break;
aOp[0].p2 = memId;
aOp[0].p3 = memId+1;
aOp[0].p3 = memId+2;
aOp[2].p3 = memId;
aOp[3].p1 = memId-1;
aOp[3].p3 = memId;
aOp[3].p5 = SQLITE_JUMPIFNULL;
aOp[4].p2 = memId+1;
aOp[5].p3 = memId;
aOp[8].p2 = memId;
aOp[6].p1 = memId;
aOp[7].p2 = memId+2;
aOp[7].p1 = memId;
aOp[10].p2 = memId;
}
}
@@ -343,6 +349,8 @@ static SQLITE_NOINLINE void autoIncrementEnd(Parse *pParse){
iRec = sqlite3GetTempReg(pParse);
assert( sqlite3SchemaMutexHeld(db, 0, pDb->pSchema) );
sqlite3VdbeAddOp3(v, OP_Le, memId+2, sqlite3VdbeCurrentAddr(v)+7, memId);
VdbeCoverage(v);
sqlite3OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenWrite);
aOp = sqlite3VdbeAddOpList(v, ArraySize(autoIncEnd), autoIncEnd, iLn);
if( aOp==0 ) break;