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Overview
| Comment: | An optimization that converts "a IN (b)" into "a==b". Seems to work, but needs additional test cases. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | degenerate_IN |
| Files: | files | file ages | folders |
| SHA1: |
8b4c3c5e506267c18550063cb9bd9351 |
| User & Date: | drh 2012-10-16 21:08:03 |
Context
|
2012-10-16
| ||
| 21:08 | An optimization that converts "a IN (b)" into "a==b". Seems to work, but needs additional test cases. Leaf check-in: 8b4c3c5e user: drh tags: degenerate_IN | |
|
2012-10-15
| ||
| 20:28 | Correct comments and enhance readability of the mkvsix tool. check-in: 2c3af657 user: mistachkin tags: trunk | |
Changes
Changes to src/parse.y.
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A.zEnd = Y.zEnd;
}
%ifndef SQLITE_OMIT_SUBQUERY
%type in_op {int}
in_op(A) ::= IN. {A = 0;}
in_op(A) ::= NOT IN. {A = 1;}
expr(A) ::= expr(X) in_op(N) LP exprlist(Y) RP(E). [IN] {
if( Y==0 ){
/* Expressions of the form
**
** expr1 IN ()
** expr1 NOT IN ()
**
** simplify to constants 0 (false) and 1 (true), respectively,
** regardless of the value of expr1.
*/
A.pExpr = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &sqlite3IntTokens[N]);
sqlite3ExprDelete(pParse->db, X.pExpr);
}else{
A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
if( A.pExpr ){
A.pExpr->x.pList = Y;
sqlite3ExprSetHeight(pParse, A.pExpr);
}else{
sqlite3ExprListDelete(pParse->db, Y);
}
if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
}
A.zStart = X.zStart;
A.zEnd = &E.z[E.n];
}
expr(A) ::= LP(B) select(X) RP(E). {
|
> > | | > > > > > > > > > > | | |
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A.zEnd = Y.zEnd;
}
%ifndef SQLITE_OMIT_SUBQUERY
%type in_op {int}
in_op(A) ::= IN. {A = 0;}
in_op(A) ::= NOT IN. {A = 1;}
expr(A) ::= expr(X) in_op(N) LP exprlist(Y) RP(E). [IN] {
sqlite3 *db = pParse->db;
ExprList *pY = Y;
if( pY==0 ){
/* Expressions of the form
**
** expr1 IN ()
** expr1 NOT IN ()
**
** simplify to constants 0 (false) and 1 (true), respectively,
** regardless of the value of expr1.
*/
A.pExpr = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &sqlite3IntTokens[N]);
sqlite3ExprDelete(db, X.pExpr);
}else if( pY->nExpr==1 ){
/* If the RHS of the IN operator has a single term, simplify as follows:
**
** expr1 IN (Y) --> expr1 = Y
** expr1 NOT IN (Y) --> expr1 <> Y
*/
assert( TK_EQ==TK_NE+1 );
A.pExpr = sqlite3PExpr(pParse, TK_EQ-N, X.pExpr, pY->a[0].pExpr, 0);
pY->a[0].pExpr = 0;
sqlite3ExprListDelete(db, pY);
}else{
A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
if( A.pExpr ){
A.pExpr->x.pList = pY;
sqlite3ExprSetHeight(pParse, A.pExpr);
}else{
sqlite3ExprListDelete(pParse->db, pY);
}
if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
}
A.zStart = X.zStart;
A.zEnd = &E.z[E.n];
}
expr(A) ::= LP(B) select(X) RP(E). {
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