/*
** Return a pointer corresponding to database zDb (i.e. "main", "temp")
** in connection handle pDb. If such a database cannot be found, return
** a NULL pointer and write an error message to pErrorDb.
**
** If the "temp" database is requested, it may need to be opened by this
** function. If an error occurs while doing so, return 0 and write an
** error message to pErrorDb.
*/
static Btree *findBtree(sqlite3 *pErrorDb, sqlite3 *pDb, const char *zDb){
int i = sqlite3FindDbName(pDb, zDb);
if( i==1 ){
Parse *pParse;
int rc = 0;
pParse = sqlite3StackAllocZero(pErrorDb, sizeof(*pParse));
if( pParse==0 ){
sqlite3Error(pErrorDb, SQLITE_NOMEM, "out of memory");
rc = SQLITE_NOMEM;
}else{
pParse->db = pDb;
if( sqlite3OpenTempDatabase(pParse) ){
sqlite3ErrorClear(pParse);
sqlite3Error(pErrorDb, pParse->rc, "%s", pParse->zErrMsg);
rc = SQLITE_ERROR;
}
sqlite3StackFree(pErrorDb, pParse);
}
if( rc ){
return 0;
}
}
if( i<0 ){
sqlite3Error(pErrorDb, SQLITE_ERROR, "unknown database %s", zDb);
return 0;
}
return pDb->aDb[i].pBt;
}
/*
** pE is a pointer to an expression which is a single term in the
** ORDER BY of a compound SELECT. The expression has not been
** name resolved.
**
** At the point this routine is called, we already know that the
** ORDER BY term is not an integer index into the result set. That
** case is handled by the calling routine.
**
** Attempt to match pE against result set columns in the left-most
** SELECT statement. Return the index i of the matching column,
** as an indication to the caller that it should sort by the i-th column.
** The left-most column is 1. In other words, the value returned is the
** same integer value that would be used in the SQL statement to indicate
** the column.
**
** If there is no match, return 0. Return -1 if an error occurs.
*/
static int resolveOrderByTermToExprList(
Parse *pParse, /* Parsing context for error messages */
Select *pSelect, /* The SELECT statement with the ORDER BY clause */
Expr *pE /* The specific ORDER BY term */
){
int i; /* Loop counter */
ExprList *pEList; /* The columns of the result set */
NameContext nc; /* Name context for resolving pE */
assert( sqlite3ExprIsInteger(pE, &i)==0 );
pEList = pSelect->pEList;
/* Resolve all names in the ORDER BY term expression
*/
memset(&nc, 0, sizeof(nc));
nc.pParse = pParse;
nc.pSrcList = pSelect->pSrc;
nc.pEList = pEList;
nc.allowAgg = 1;
nc.nErr = 0;
if( sqlite3ResolveExprNames(&nc, pE) ){
sqlite3ErrorClear(pParse);
return 0;
}
/* Try to match the ORDER BY expression against an expression
** in the result set. Return an 1-based index of the matching
** result-set entry.
*/
for(i=0; i<pEList->nExpr; i++){
if( sqlite3ExprCompare(pEList->a[i].pExpr, pE) ){
return i+1;
}
}
/* If no match, return 0. */
return 0;
}
