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Revise the implementation of OP_Once so that it is smaller, faster, and uses

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less memory.  This also fixes an obscure bug introduced 3 days ago by check-in
[5990a1bdb4a073].

FossilOrigin-Name: 6bf5ba10d28f1b0a32aa9a560ae3143a1235eadb
This commit is contained in:
drh
2016-09-18 16:08:10 +00:00
parent 598f7c59e1
commit 9e5eb9c8cc
12 changed files with 53 additions and 56 deletions
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42
src/vdbe.c
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@@ -2332,22 +2332,18 @@ case OP_BitNot: { /* same as TK_BITNOT, in1, out2 */
/* Opcode: Once P1 P2 * * *
**
** Check the "once" flag number P1. If it is set, jump to instruction P2.
** Otherwise, set the flag and fall through to the next instruction.
** In other words, this opcode causes all following opcodes up through P2
** (but not including P2) to run just once and to be skipped on subsequent
** times through the loop.
**
** All "once" flags are initially cleared whenever a prepared statement
** first begins to run.
** If the P1 value is equal to the P1 value on the OP_Init opcode at
** instruction 0, then jump to P2. If the two P1 values differ, then
** set the P1 value on this opcode to equal the P1 value on the OP_Init
** and fall through.
*/
case OP_Once: { /* jump */
assert( pOp->p1<p->nOnceFlag );
VdbeBranchTaken(p->aOnceFlag[pOp->p1]!=0, 2);
if( p->aOnceFlag[pOp->p1] ){
assert( p->aOp[0].opcode==OP_Init );
VdbeBranchTaken(p->aOp[0].p1==pOp->p1, 2);
if( p->aOp[0].p1==pOp->p1 ){
goto jump_to_p2;
}else{
p->aOnceFlag[pOp->p1] = 1;
pOp->p1 = p->aOp[0].p1;
}
break;
}
@@ -5790,8 +5786,7 @@ case OP_Program: { /* jump */
if( pProgram->nCsr==0 ) nMem++;
nByte = ROUND8(sizeof(VdbeFrame))
+ nMem * sizeof(Mem)
+ pProgram->nCsr * sizeof(VdbeCursor *)
+ pProgram->nOnce * sizeof(u8);
+ pProgram->nCsr * sizeof(VdbeCursor *);
pFrame = sqlite3DbMallocZero(db, nByte);
if( !pFrame ){
goto no_mem;
@@ -5811,8 +5806,6 @@ case OP_Program: { /* jump */
pFrame->aOp = p->aOp;
pFrame->nOp = p->nOp;
pFrame->token = pProgram->token;
pFrame->aOnceFlag = p->aOnceFlag;
pFrame->nOnceFlag = p->nOnceFlag;
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
pFrame->anExec = p->anExec;
#endif
@@ -5846,13 +5839,10 @@ case OP_Program: { /* jump */
p->apCsr = (VdbeCursor **)&aMem[p->nMem];
p->aOp = aOp = pProgram->aOp;
p->nOp = pProgram->nOp;
p->aOnceFlag = (u8 *)&p->apCsr[p->nCursor];
p->nOnceFlag = pProgram->nOnce;
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
p->anExec = 0;
#endif
pOp = &aOp[-1];
memset(p->aOnceFlag, 0, p->nOnceFlag);
break;
}
@@ -6819,7 +6809,7 @@ case OP_MaxPgcnt: { /* out2 */
#endif
/* Opcode: Init * P2 * P4 *
/* Opcode: Init P1 P2 * P4 *
** Synopsis: Start at P2
**
** Programs contain a single instance of this opcode as the very first
@@ -6830,9 +6820,13 @@ case OP_MaxPgcnt: { /* out2 */
** Or if P4 is blank, use the string returned by sqlite3_sql().
**
** If P2 is not zero, jump to instruction P2.
**
** Increment the value of P1 so that OP_Once opcodes will jump the
** first time they are evaluated for this run.
*/
case OP_Init: { /* jump */
char *zTrace;
int i;
/* If the P4 argument is not NULL, then it must be an SQL comment string.
** The "--" string is broken up to prevent false-positives with srcck1.c.
@@ -6844,6 +6838,7 @@ case OP_Init: { /* jump */
** sqlite3_expanded_sql(P) otherwise.
*/
assert( pOp->p4.z==0 || strncmp(pOp->p4.z, "-" "- ", 3)==0 );
assert( pOp==p->aOp ); /* Always instruction 0 */
#ifndef SQLITE_OMIT_TRACE
if( (db->mTrace & (SQLITE_TRACE_STMT|SQLITE_TRACE_LEGACY))!=0
@@ -6881,6 +6876,13 @@ case OP_Init: { /* jump */
#endif /* SQLITE_DEBUG */
#endif /* SQLITE_OMIT_TRACE */
assert( pOp->p2>0 );
if( pOp->p1>=sqlite3GlobalConfig.iOnceResetThreshold ){
for(i=1; i<p->nOp; i++){
if( p->aOp[i].opcode==OP_Once ) p->aOp[i].p1 = 0;
}
pOp->p1 = 0;
}
pOp->p1++;
goto jump_to_p2;
}