/*
** Implementation of the non-aggregate min() and max() functions
*/
static void minmaxFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
int i;
int mask; /* 0 for min() or 0xffffffff for max() */
int iBest;
CollSeq *pColl;
if( argc==0 ) return;
mask = sqlite3_user_data(context)==0 ? 0 : -1;
pColl = sqlite3GetFuncCollSeq(context);
assert( pColl );
assert( mask==-1 || mask==0 );
iBest = 0;
if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
for(i=1; i<argc; i++){
if( sqlite3_value_type(argv[i])==SQLITE_NULL ) return;
if( (sqlite3MemCompare(argv[iBest], argv[i], pColl)^mask)>=0 ){
iBest = i;
}
}
sqlite3_result_value(context, argv[iBest]);
}
/*
** Routines to implement min() and max() aggregate functions.
*/
static void minmaxStep(
sqlite3_context *context,
int NotUsed,
sqlite3_value **argv
){
Mem *pArg = (Mem *)argv[0];
Mem *pBest;
UNUSED_PARAMETER(NotUsed);
if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
pBest = (Mem *)sqlite3_aggregate_context(context, sizeof(*pBest));
if( !pBest ) return;
if( pBest->flags ){
int max;
int cmp;
CollSeq *pColl = sqlite3GetFuncCollSeq(context);
/* This step function is used for both the min() and max() aggregates,
** the only difference between the two being that the sense of the
** comparison is inverted. For the max() aggregate, the
** sqlite3_user_data() function returns (void *)-1. For min() it
** returns (void *)db, where db is the sqlite3* database pointer.
** Therefore the next statement sets variable 'max' to 1 for the max()
** aggregate, or 0 for min().
*/
max = sqlite3_user_data(context)!=0;
cmp = sqlite3MemCompare(pBest, pArg, pColl);
if( (max && cmp<0) || (!max && cmp>0) ){
sqlite3VdbeMemCopy(pBest, pArg);
}
}else{
sqlite3VdbeMemCopy(pBest, pArg);
}
}
/*
** Implementation of the NULLIF(x,y) function. The result is the first
** argument if the arguments are different. The result is NULL if the
** arguments are equal to each other.
*/
static void nullifFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
CollSeq *pColl = sqlite3GetFuncCollSeq(context);
if( sqlite3MemCompare(argv[0], argv[1], pColl)!=0 ){
sqlite3_result_value(context, argv[0]);
}
}
/*
** Implementation of the NULLIF(x,y) function. The result is the first
** argument if the arguments are different. The result is NULL if the
** arguments are equal to each other.
*/
static void nullifFunc(
sqlite3_context *context,
int NotUsed,
sqlite3_value **argv
){
CollSeq *pColl = sqlite3GetFuncCollSeq(context);
UNUSED_PARAMETER(NotUsed);
if( sqlite3MemCompare(argv[0], argv[1], pColl)!=0 ){
sqlite3_result_value(context, argv[0]);
}
}
