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Allow virtual table implementations to overload function that use

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a column of the virtual table as their first argument.  Untested. (CVS 3322)

FossilOrigin-Name: 12cc7af4b6b8b4f1a43d962fbafde8cba683a907
This commit is contained in:
drh
2006-07-08 17:06:43 +00:00
parent 4144905b53
commit b7f6f68f3a
10 changed files with 117 additions and 23 deletions
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62
src/vtab.c
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@@ -11,7 +11,7 @@
*************************************************************************
** This file contains code used to help implement virtual tables.
**
** $Id: vtab.c,v 1.25 2006/06/26 11:17:51 danielk1977 Exp $
** $Id: vtab.c,v 1.26 2006/07/08 17:06:44 drh Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"
@@ -573,4 +573,64 @@ int sqlite3VtabBegin(sqlite3 *db, sqlite3_vtab *pVtab){
return rc;
}
/*
** The first parameter (pDef) is a function implementation. The
** second parameter (pExpr) is the first argument to this function.
** If pExpr is a column in a virtual table, then let the virtual
** table implementation have an opportunity to overload the function.
**
** This routine is used to allow virtual table implementations to
** overload MATCH, LIKE, GLOB, and REGEXP operators.
**
** Return either the pDef argument (indicating no change) or a
** new FuncDef structure that is marked as ephemeral using the
** SQLITE_FUNC_EPHEM flag.
*/
FuncDef *sqlite3VtabOverloadFunction(
FuncDef *pDef, /* Function to possibly overload */
int nArg, /* Number of arguments to the function */
Expr *pExpr /* First argument to the function */
){
Table *pTab;
sqlite3_vtab *pVtab;
sqlite3_module *pMod;
int (*xFunc)(sqlite3_context*,int,sqlite3_value**);
void *pArg;
int iEnc;
int rc;
FuncDef *pNew;
/* Check to see the left operand is a column in a virtual table */
if( pExpr==0 ) return pDef;
if( pExpr->op!=TK_COLUMN ) return pDef;
pTab = pExpr->pTab;
if( pTab==0 ) return pDef;
if( !pTab->isVirtual ) return pDef;
pVtab = pTab->pVtab;
assert( pVtab!=0 );
assert( pVtab->pModule!=0 );
pMod = pVtab->pModule;
if( pMod->xFindFunction==0 ) return pDef;
/* Call the xFuncFunction method on the virtual table implementation
** to see if the implementation wants to overload this function */
if( pMod->xFindFunction(pVtab, nArg, pDef->zName, &xFunc, &pArg, &iEnc)==0 ){
return pDef;
}
/* Create a new ephemeral function definition for the overloaded
** function */
pNew = sqliteMalloc( sizeof(*pNew) + strlen(pDef->zName) );
if( pNew==0 ){
return pDef;
}
*pNew = *pDef;
strcpy(pNew->zName, pDef->zName);
pNew->xFunc = xFunc;
pNew->pUserData = pArg;
pNew->iPrefEnc = iEnc;
pNew->flags |= SQLITE_FUNC_EPHEM;
return pNew;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */