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COALESCE() and NULLIF() are now first-class expressions, not macros

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that turn into CASE expressions.  They evaluate their arguments at most
once.  Patch by Kris Jurka, review and (very light) editorializing by me.
This commit is contained in:
Tom Lane
2003-02-16 02:30:39 +00:00
parent de25638d2f
commit 51972a9d5d
22 changed files with 644 additions and 107 deletions
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140
src/backend/executor/execQual.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/execQual.c,v 1.124 2003/02/03 21:15:43 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/execQual.c,v 1.125 2003/02/16 02:30:37 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -64,7 +64,7 @@ static Datum ExecEvalFunc(FuncExprState *fcache, ExprContext *econtext,
static Datum ExecEvalOper(FuncExprState *fcache, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalDistinct(FuncExprState *fcache, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone);
bool *isNull);
static ExprDoneCond ExecEvalFuncArgs(FunctionCallInfo fcinfo,
List *argList, ExprContext *econtext);
static Datum ExecEvalNot(BoolExprState *notclause, ExprContext *econtext,
@ -75,6 +75,11 @@ static Datum ExecEvalAnd(BoolExprState *andExpr, ExprContext *econtext,
bool *isNull);
static Datum ExecEvalCase(CaseExprState *caseExpr, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalCoalesce(CoalesceExprState *coalesceExpr,
ExprContext *econtext,
bool *isNull);
static Datum ExecEvalNullIf(FuncExprState *nullIfExpr, ExprContext *econtext,
bool *isNull);
static Datum ExecEvalNullTest(GenericExprState *nstate,
ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone);
@ -1187,8 +1192,7 @@ ExecEvalOper(FuncExprState *fcache,
static Datum
ExecEvalDistinct(FuncExprState *fcache,
ExprContext *econtext,
bool *isNull,
ExprDoneCond *isDone)
bool *isNull)
{
Datum result;
FunctionCallInfoData fcinfo;
@ -1370,6 +1374,7 @@ ExecEvalAnd(BoolExprState *andExpr, ExprContext *econtext, bool *isNull)
return BoolGetDatum(!AnyNull);
}
/* ----------------------------------------------------------------
* ExecEvalCase
*
@ -1429,6 +1434,91 @@ ExecEvalCase(CaseExprState *caseExpr, ExprContext *econtext,
return (Datum) 0;
}
/* ----------------------------------------------------------------
* ExecEvalCoalesce
* ----------------------------------------------------------------
*/
static Datum
ExecEvalCoalesce(CoalesceExprState *coalesceExpr, ExprContext *econtext,
bool *isNull)
{
List *arg;
/* Simply loop through until something NOT NULL is found */
foreach(arg, coalesceExpr->args)
{
ExprState *e = (ExprState *) lfirst(arg);
Datum value;
value = ExecEvalExpr(e, econtext, isNull, NULL);
if (!*isNull)
return value;
}
/* Else return NULL */
*isNull = true;
return (Datum) 0;
}
/* ----------------------------------------------------------------
* ExecEvalNullIf
*
* Note that this is *always* derived from the equals operator,
* but since we need special processing of the arguments
* we can not simply reuse ExecEvalOper() or ExecEvalFunc().
* ----------------------------------------------------------------
*/
static Datum
ExecEvalNullIf(FuncExprState *fcache, ExprContext *econtext,
bool *isNull)
{
Datum result;
FunctionCallInfoData fcinfo;
ExprDoneCond argDone;
List *argList;
/*
* Initialize function cache if first time through
*/
if (fcache->func.fn_oid == InvalidOid)
{
NullIfExpr *op = (NullIfExpr *) fcache->xprstate.expr;
init_fcache(op->opfuncid, fcache, econtext->ecxt_per_query_memory);
Assert(!fcache->func.fn_retset);
}
/*
* extract info from fcache
*/
argList = fcache->args;
/* Need to prep callinfo structure */
MemSet(&fcinfo, 0, sizeof(fcinfo));
fcinfo.flinfo = &(fcache->func);
argDone = ExecEvalFuncArgs(&fcinfo, argList, econtext);
if (argDone != ExprSingleResult)
elog(ERROR, "NULLIF does not support set arguments");
Assert(fcinfo.nargs == 2);
/* if either argument is NULL they can't be equal */
if (!fcinfo.argnull[0] && !fcinfo.argnull[1])
{
fcinfo.isnull = false;
result = FunctionCallInvoke(&fcinfo);
/* if the arguments are equal return null */
if (!fcinfo.isnull && DatumGetBool(result))
{
*isNull = true;
return (Datum) 0;
}
}
/* else return first argument */
*isNull = fcinfo.argnull[0];
return fcinfo.arg[0];
}
/* ----------------------------------------------------------------
* ExecEvalNullTest
*
@ -1778,7 +1868,7 @@ ExecEvalExpr(ExprState *expression,
break;
case T_DistinctExpr:
retDatum = ExecEvalDistinct((FuncExprState *) expression, econtext,
isNull, isDone);
isNull);
break;
case T_BoolExpr:
{
@ -1826,6 +1916,16 @@ ExecEvalExpr(ExprState *expression,
isNull,
isDone);
break;
case T_CoalesceExpr:
retDatum = ExecEvalCoalesce((CoalesceExprState *) expression,
econtext,
isNull);
break;
case T_NullIfExpr:
retDatum = ExecEvalNullIf((FuncExprState *) expression,
econtext,
isNull);
break;
case T_NullTest:
retDatum = ExecEvalNullTest((GenericExprState *) expression,
econtext,
@ -2082,6 +2182,36 @@ ExecInitExpr(Expr *node, PlanState *parent)
state = (ExprState *) cstate;
}
break;
case T_CoalesceExpr:
{
CoalesceExpr *coalesceexpr = (CoalesceExpr *) node;
CoalesceExprState *cstate = makeNode(CoalesceExprState);
List *outlist = NIL;
List *inlist;
foreach(inlist, coalesceexpr->args)
{
Expr *e = (Expr *) lfirst(inlist);
ExprState *estate;
estate = ExecInitExpr(e, parent);
outlist = lappend(outlist, estate);
}
cstate->args = outlist;
state = (ExprState *) cstate;
}
break;
case T_NullIfExpr:
{
NullIfExpr *nullifexpr = (NullIfExpr *) node;
FuncExprState *fstate = makeNode(FuncExprState);
fstate->args = (List *)
ExecInitExpr((Expr *) nullifexpr->args, parent);
fstate->func.fn_oid = InvalidOid; /* not initialized */
state = (ExprState *) fstate;
}
break;
case T_NullTest:
{
NullTest *ntest = (NullTest *) node;