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Enhance the like optimization so that it works with an ESCAPE clause.

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FossilOrigin-Name: f5d330f495d07a704e115595bbdf5422ddb68fd8191114c5a12c9c873d983f7c
This commit is contained in:
drh
2017-07-27 20:24:29 +00:00
parent 01d837df9c
commit 1d42ea71c2
6 changed files with 112 additions and 22 deletions
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30
src/func.c
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@@ -1706,9 +1706,14 @@ void sqlite3RegisterLikeFunctions(sqlite3 *db, int caseSensitive){
/*
** pExpr points to an expression which implements a function. If
** it is appropriate to apply the LIKE optimization to that function
** then set aWc[0] through aWc[2] to the wildcard characters and
** return TRUE. If the function is not a LIKE-style function then
** return FALSE.
** then set aWc[0] through aWc[2] to the wildcard characters and the
** escape character and then return TRUE. If the function is not a
** LIKE-style function then return FALSE.
**
** The expression "a LIKE b ESCAPE c" is only considered a valid LIKE
** operator if c is a string literal that is exactly one byte in length.
** That one byte is stored in aWc[3]. aWc[3] is set to zero if there is
** no ESCAPE clause.
**
** *pIsNocase is set to true if uppercase and lowercase are equivalent for
** the function (default for LIKE). If the function makes the distinction
@@ -1717,17 +1722,26 @@ void sqlite3RegisterLikeFunctions(sqlite3 *db, int caseSensitive){
*/
int sqlite3IsLikeFunction(sqlite3 *db, Expr *pExpr, int *pIsNocase, char *aWc){
FuncDef *pDef;
if( pExpr->op!=TK_FUNCTION
|| !pExpr->x.pList
|| pExpr->x.pList->nExpr!=2
){
int nExpr;
if( pExpr->op!=TK_FUNCTION || !pExpr->x.pList ){
return 0;
}
assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
pDef = sqlite3FindFunction(db, pExpr->u.zToken, 2, SQLITE_UTF8, 0);
nExpr = pExpr->x.pList->nExpr;
pDef = sqlite3FindFunction(db, pExpr->u.zToken, nExpr, SQLITE_UTF8, 0);
if( NEVER(pDef==0) || (pDef->funcFlags & SQLITE_FUNC_LIKE)==0 ){
return 0;
}
if( nExpr<3 ){
aWc[3] = 0;
}else{
Expr *pEscape = pExpr->x.pList->a[2].pExpr;
char *zEscape;
if( pEscape->op!=TK_STRING ) return 0;
zEscape = pEscape->u.zToken;
if( zEscape[0]==0 || zEscape[1]!=0 ) return 0;
aWc[3] = zEscape[0];
}
/* The memcpy() statement assumes that the wildcard characters are
** the first three statements in the compareInfo structure. The