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Improvements to IN operator code generator comments. Avoid unnecessary

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Copy operations on the LHS of the IN operator.

FossilOrigin-Name: b6344298783a1207cba3f635939ddc9ba922ab67
This commit is contained in:
drh
2016-08-25 15:46:25 +00:00
parent ee0f22fd3b
commit ecb87ac88d
3 changed files with 42 additions and 26 deletions
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54
src/expr.c
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@@ -2637,16 +2637,19 @@ int sqlite3ExprCheckIN(Parse *pParse, Expr *pIn){
** x IN (SELECT ...)
** x IN (value, value, ...)
**
** The left-hand side (LHS) is a scalar expression. The right-hand side (RHS)
** is an array of zero or more values. The expression is true if the LHS is
** contained within the RHS. The value of the expression is unknown (NULL)
** if the LHS is NULL or if the LHS is not contained within the RHS and the
** RHS contains one or more NULL values.
** The left-hand side (LHS) is a scalar or vector expression. The
** right-hand side (RHS) is an array of zero or more values. The IN operator
** is true if the LHS is contained within the RHS. The result is false
** if the LHS is definitely not in the RHS. The result is NULL if the presence
** of the LHS in the RHS cannot be determined due to NULLs.
**
** This routine generates code that jumps to destIfFalse if the LHS is not
** contained within the RHS. If due to NULLs we cannot determine if the LHS
** is contained in the RHS then jump to destIfNull. If the LHS is contained
** within the RHS then fall through.
**
** See the separate in-operator.md documentation file in the canonical
** SQLite source tree for additional information.
*/
static void sqlite3ExprCodeIN(
Parse *pParse, /* Parsing and code generating context */
@@ -2660,22 +2663,18 @@ static void sqlite3ExprCodeIN(
Vdbe *v; /* Statement under construction */
int *aiMap = 0; /* Map from vector field to index column */
char *zAff = 0; /* Affinity string for comparisons */
int nVector; /* Size of vectors for this IN(...) op */
int iDummy; /* Dummy parameter to exprCodeVector() */
Expr *pLeft = pExpr->pLeft;
int i;
int nVector; /* Size of vectors for this IN operator */
int iDummy; /* Dummy parameter to exprCodeVector() */
Expr *pLeft = pExpr->pLeft; /* The LHS of the IN operator */
int i; /* loop counter */
if( sqlite3ExprCheckIN(pParse, pExpr) ) return;
zAff = exprINAffinity(pParse, pExpr);
if( zAff==0 ) return;
nVector = sqlite3ExprVectorSize(pExpr->pLeft);
aiMap = (int*)sqlite3DbMallocZero(
pParse->db, nVector*(sizeof(int) + sizeof(char)) + 1
);
if( aiMap==0 ){
sqlite3DbFree(pParse->db, zAff);
return;
}
if( pParse->db->mallocFailed ) goto end_code_IN_op;
/* Attempt to compute the RHS. After this step, if anything other than
** IN_INDEX_NOOP is returned, the table opened ith cursor pExpr->iTable
@@ -2691,16 +2690,32 @@ static void sqlite3ExprCodeIN(
assert( pParse->nErr || nVector==1 || eType==IN_INDEX_EPH
|| eType==IN_INDEX_INDEX_ASC || eType==IN_INDEX_INDEX_DESC
);
#ifdef SQLITE_DEBUG
/* Confirm that aiMap[] contains nVector integer values between 0 and
** nVector-1. */
for(i=0; i<nVector; i++){
int j, cnt;
for(cnt=j=0; j<nVector; j++) if( aiMap[j]==i ) cnt++;
assert( cnt==1 );
}
#endif
/* Code the LHS, the <expr> from "<expr> IN (...)". If the LHS is a
** vector, then it is stored in an array of nVector registers starting
** at r1.
*/
r1 = sqlite3GetTempRange(pParse, nVector);
sqlite3ExprCachePush(pParse);
r2 = exprCodeVector(pParse, pLeft, &iDummy);
for(i=0; i<nVector; i++){
sqlite3VdbeAddOp3(v, OP_Copy, r2+i, r1+aiMap[i], 0);
for(i=0; i<nVector && aiMap[i]==i; i++){}
if( i==nVector ){
/* LHS fields are already in the correct order */
r1 = r2;
}else{
/* Need to reorder the LHS fields according to aiMap */
r1 = sqlite3GetTempRange(pParse, nVector);
for(i=0; i<nVector; i++){
sqlite3VdbeAddOp3(v, OP_Copy, r2+i, r1+aiMap[i], 0);
}
}
/* If sqlite3FindInIndex() did not find or create an index that is
@@ -2861,11 +2876,12 @@ static void sqlite3ExprCodeIN(
}
}
}
sqlite3ReleaseTempReg(pParse, r1);
if( r2!=r1 ) sqlite3ReleaseTempReg(pParse, r1);
sqlite3ExprCachePop(pParse);
VdbeComment((v, "end IN expr"));
end_code_IN_op:
sqlite3DbFree(pParse->db, aiMap);
sqlite3DbFree(pParse->db, zAff);
VdbeComment((v, "end IN expr"));
}
#endif /* SQLITE_OMIT_SUBQUERY */