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COALESCE() and NULLIF() are now first-class expressions, not macros
that turn into CASE expressions. They evaluate their arguments at most once. Patch by Kris Jurka, review and (very light) editorializing by me.
1 parent de25638 commit 51972a9

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22 files changed

+645
-108
lines changed

22 files changed

+645
-108
lines changed

‎doc/src/sgml/func.sgml

Lines changed: 1 addition & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.139 2003/02/13 05:24:01 momjian Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.140 2003/02/16 02:30:36 tgl Exp $
33
PostgreSQL documentation
44
-->
55

@@ -6295,17 +6295,6 @@ SELECT NULLIF(value, '(none)') ...
62956295
</programlisting>
62966296
</para>
62976297

6298-
<tip>
6299-
<para>
6300-
<function>COALESCE</function> and <function>NULLIF</function> are
6301-
just shorthand for <token>CASE</token> expressions. They are actually
6302-
converted into <token>CASE</token> expressions at a very early stage
6303-
of processing, and subsequent processing thinks it is dealing with
6304-
<token>CASE</token>. Thus an incorrect <function>COALESCE</function> or
6305-
<function>NULLIF</function> usage may draw an error message that
6306-
refers to <token>CASE</token>.
6307-
</para>
6308-
</tip>
63096298
</sect2>
63106299

63116300
</sect1>

‎src/backend/catalog/dependency.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.21 2003/02/09 06:56:26 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.22 2003/02/16 02:30:37 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -933,6 +933,14 @@ find_expr_references_walker(Node *node,
933933
&context->addrs);
934934
/* fall through to examine arguments */
935935
}
936+
if (IsA(node, NullIfExpr))
937+
{
938+
NullIfExpr *nullifexpr = (NullIfExpr *) node;
939+
940+
add_object_address(OCLASS_OPERATOR, nullifexpr->opno, 0,
941+
&context->addrs);
942+
/* fall through to examine arguments */
943+
}
936944
if (IsA(node, Aggref))
937945
{
938946
Aggref *aggref = (Aggref *) node;

‎src/backend/executor/execQual.c

Lines changed: 135 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/executor/execQual.c,v 1.124 2003/02/03 21:15:43 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/executor/execQual.c,v 1.125 2003/02/16 02:30:37 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -64,7 +64,7 @@ static Datum ExecEvalFunc(FuncExprState *fcache, ExprContext *econtext,
6464
static Datum ExecEvalOper(FuncExprState *fcache, ExprContext *econtext,
6565
bool *isNull, ExprDoneCond *isDone);
6666
static Datum ExecEvalDistinct(FuncExprState *fcache, ExprContext *econtext,
67-
bool *isNull, ExprDoneCond *isDone);
67+
bool *isNull);
6868
static ExprDoneCond ExecEvalFuncArgs(FunctionCallInfo fcinfo,
6969
List *argList, ExprContext *econtext);
7070
static Datum ExecEvalNot(BoolExprState *notclause, ExprContext *econtext,
@@ -75,6 +75,11 @@ static Datum ExecEvalAnd(BoolExprState *andExpr, ExprContext *econtext,
7575
bool *isNull);
7676
static Datum ExecEvalCase(CaseExprState *caseExpr, ExprContext *econtext,
7777
bool *isNull, ExprDoneCond *isDone);
78+
static Datum ExecEvalCoalesce(CoalesceExprState *coalesceExpr,
79+
ExprContext *econtext,
80+
bool *isNull);
81+
static Datum ExecEvalNullIf(FuncExprState *nullIfExpr, ExprContext *econtext,
82+
bool *isNull);
7883
static Datum ExecEvalNullTest(GenericExprState *nstate,
7984
ExprContext *econtext,
8085
bool *isNull, ExprDoneCond *isDone);
@@ -1187,8 +1192,7 @@ ExecEvalOper(FuncExprState *fcache,
11871192
static Datum
11881193
ExecEvalDistinct(FuncExprState *fcache,
11891194
ExprContext *econtext,
1190-
bool *isNull,
1191-
ExprDoneCond *isDone)
1195+
bool *isNull)
11921196
{
11931197
Datum result;
11941198
FunctionCallInfoData fcinfo;
@@ -1370,6 +1374,7 @@ ExecEvalAnd(BoolExprState *andExpr, ExprContext *econtext, bool *isNull)
13701374
return BoolGetDatum(!AnyNull);
13711375
}
13721376

1377+
13731378
/* ----------------------------------------------------------------
13741379
* ExecEvalCase
13751380
*
@@ -1429,6 +1434,91 @@ ExecEvalCase(CaseExprState *caseExpr, ExprContext *econtext,
14291434
return (Datum) 0;
14301435
}
14311436

1437+
/* ----------------------------------------------------------------
1438+
* ExecEvalCoalesce
1439+
* ----------------------------------------------------------------
1440+
*/
1441+
static Datum
1442+
ExecEvalCoalesce(CoalesceExprState *coalesceExpr, ExprContext *econtext,
1443+
bool *isNull)
1444+
{
1445+
List *arg;
1446+
1447+
/* Simply loop through until something NOT NULL is found */
1448+
foreach(arg, coalesceExpr->args)
1449+
{
1450+
ExprState *e = (ExprState *) lfirst(arg);
1451+
Datum value;
1452+
1453+
value = ExecEvalExpr(e, econtext, isNull, NULL);
1454+
if (!*isNull)
1455+
return value;
1456+
}
1457+
1458+
/* Else return NULL */
1459+
*isNull = true;
1460+
return (Datum) 0;
1461+
}
1462+
1463+
/* ----------------------------------------------------------------
1464+
* ExecEvalNullIf
1465+
*
1466+
* Note that this is *always* derived from the equals operator,
1467+
* but since we need special processing of the arguments
1468+
* we can not simply reuse ExecEvalOper() or ExecEvalFunc().
1469+
* ----------------------------------------------------------------
1470+
*/
1471+
static Datum
1472+
ExecEvalNullIf(FuncExprState *fcache, ExprContext *econtext,
1473+
bool *isNull)
1474+
{
1475+
Datum result;
1476+
FunctionCallInfoData fcinfo;
1477+
ExprDoneCond argDone;
1478+
List *argList;
1479+
1480+
/*
1481+
* Initialize function cache if first time through
1482+
*/
1483+
if (fcache->func.fn_oid == InvalidOid)
1484+
{
1485+
NullIfExpr *op = (NullIfExpr *) fcache->xprstate.expr;
1486+
1487+
init_fcache(op->opfuncid, fcache, econtext->ecxt_per_query_memory);
1488+
Assert(!fcache->func.fn_retset);
1489+
}
1490+
1491+
/*
1492+
* extract info from fcache
1493+
*/
1494+
argList = fcache->args;
1495+
1496+
/* Need to prep callinfo structure */
1497+
MemSet(&fcinfo, 0, sizeof(fcinfo));
1498+
fcinfo.flinfo = &(fcache->func);
1499+
argDone = ExecEvalFuncArgs(&fcinfo, argList, econtext);
1500+
if (argDone != ExprSingleResult)
1501+
elog(ERROR, "NULLIF does not support set arguments");
1502+
Assert(fcinfo.nargs == 2);
1503+
1504+
/* if either argument is NULL they can't be equal */
1505+
if (!fcinfo.argnull[0] && !fcinfo.argnull[1])
1506+
{
1507+
fcinfo.isnull = false;
1508+
result = FunctionCallInvoke(&fcinfo);
1509+
/* if the arguments are equal return null */
1510+
if (!fcinfo.isnull && DatumGetBool(result))
1511+
{
1512+
*isNull = true;
1513+
return (Datum) 0;
1514+
}
1515+
}
1516+
1517+
/* else return first argument */
1518+
*isNull = fcinfo.argnull[0];
1519+
return fcinfo.arg[0];
1520+
}
1521+
14321522
/* ----------------------------------------------------------------
14331523
* ExecEvalNullTest
14341524
*
@@ -1778,7 +1868,7 @@ ExecEvalExpr(ExprState *expression,
17781868
break;
17791869
case T_DistinctExpr:
17801870
retDatum = ExecEvalDistinct((FuncExprState *) expression, econtext,
1781-
isNull, isDone);
1871+
isNull);
17821872
break;
17831873
case T_BoolExpr:
17841874
{
@@ -1826,6 +1916,16 @@ ExecEvalExpr(ExprState *expression,
18261916
isNull,
18271917
isDone);
18281918
break;
1919+
case T_CoalesceExpr:
1920+
retDatum = ExecEvalCoalesce((CoalesceExprState *) expression,
1921+
econtext,
1922+
isNull);
1923+
break;
1924+
case T_NullIfExpr:
1925+
retDatum = ExecEvalNullIf((FuncExprState *) expression,
1926+
econtext,
1927+
isNull);
1928+
break;
18291929
case T_NullTest:
18301930
retDatum = ExecEvalNullTest((GenericExprState *) expression,
18311931
econtext,
@@ -2082,6 +2182,36 @@ ExecInitExpr(Expr *node, PlanState *parent)
20822182
state = (ExprState *) cstate;
20832183
}
20842184
break;
2185+
case T_CoalesceExpr:
2186+
{
2187+
CoalesceExpr *coalesceexpr = (CoalesceExpr *) node;
2188+
CoalesceExprState *cstate = makeNode(CoalesceExprState);
2189+
List *outlist = NIL;
2190+
List *inlist;
2191+
2192+
foreach(inlist, coalesceexpr->args)
2193+
{
2194+
Expr *e = (Expr *) lfirst(inlist);
2195+
ExprState *estate;
2196+
2197+
estate = ExecInitExpr(e, parent);
2198+
outlist = lappend(outlist, estate);
2199+
}
2200+
cstate->args = outlist;
2201+
state = (ExprState *) cstate;
2202+
}
2203+
break;
2204+
case T_NullIfExpr:
2205+
{
2206+
NullIfExpr *nullifexpr = (NullIfExpr *) node;
2207+
FuncExprState *fstate = makeNode(FuncExprState);
2208+
2209+
fstate->args = (List *)
2210+
ExecInitExpr((Expr *) nullifexpr->args, parent);
2211+
fstate->func.fn_oid = InvalidOid; /* not initialized */
2212+
state = (ExprState *) fstate;
2213+
}
2214+
break;
20852215
case T_NullTest:
20862216
{
20872217
NullTest *ntest = (NullTest *) node;

‎src/backend/nodes/copyfuncs.c

Lines changed: 39 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@
1515
* Portions Copyright (c) 1994, Regents of the University of California
1616
*
1717
* IDENTIFICATION
18-
* $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.243 2003/02/10 04:44:44 tgl Exp $
18+
* $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.244 2003/02/16 02:30:37 tgl Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
@@ -785,7 +785,7 @@ _copyOpExpr(OpExpr *from)
785785
}
786786

787787
/*
788-
* _copyDistinctExpr
788+
* _copyDistinctExpr (same as OpExpr)
789789
*/
790790
static DistinctExpr *
791791
_copyDistinctExpr(DistinctExpr *from)
@@ -919,6 +919,37 @@ _copyCaseWhen(CaseWhen *from)
919919
return newnode;
920920
}
921921

922+
/*
923+
* _copyCoalesceExpr
924+
*/
925+
static CoalesceExpr *
926+
_copyCoalesceExpr(CoalesceExpr *from)
927+
{
928+
CoalesceExpr *newnode = makeNode(CoalesceExpr);
929+
930+
COPY_SCALAR_FIELD(coalescetype);
931+
COPY_NODE_FIELD(args);
932+
933+
return newnode;
934+
}
935+
936+
/*
937+
* _copyNullIfExpr (same as OpExpr)
938+
*/
939+
static NullIfExpr *
940+
_copyNullIfExpr(NullIfExpr *from)
941+
{
942+
NullIfExpr *newnode = makeNode(NullIfExpr);
943+
944+
COPY_SCALAR_FIELD(opno);
945+
COPY_SCALAR_FIELD(opfuncid);
946+
COPY_SCALAR_FIELD(opresulttype);
947+
COPY_SCALAR_FIELD(opretset);
948+
COPY_NODE_FIELD(args);
949+
950+
return newnode;
951+
}
952+
922953
/*
923954
* _copyNullTest
924955
*/
@@ -2484,6 +2515,12 @@ copyObject(void *from)
24842515
case T_CaseWhen:
24852516
retval = _copyCaseWhen(from);
24862517
break;
2518+
case T_CoalesceExpr:
2519+
retval = _copyCoalesceExpr(from);
2520+
break;
2521+
case T_NullIfExpr:
2522+
retval = _copyNullIfExpr(from);
2523+
break;
24872524
case T_NullTest:
24882525
retval = _copyNullTest(from);
24892526
break;

‎src/backend/nodes/equalfuncs.c

Lines changed: 38 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@
1818
* Portions Copyright (c) 1994, Regents of the University of California
1919
*
2020
* IDENTIFICATION
21-
* $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.186 2003/02/10 04:44:45 tgl Exp $
21+
* $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.187 2003/02/16 02:30:37 tgl Exp $
2222
*
2323
*-------------------------------------------------------------------------
2424
*/
@@ -378,6 +378,37 @@ _equalCaseWhen(CaseWhen *a, CaseWhen *b)
378378
return true;
379379
}
380380

381+
static bool
382+
_equalCoalesceExpr(CoalesceExpr *a, CoalesceExpr *b)
383+
{
384+
COMPARE_SCALAR_FIELD(coalescetype);
385+
COMPARE_NODE_FIELD(args);
386+
387+
return true;
388+
}
389+
390+
static bool
391+
_equalNullIfExpr(NullIfExpr *a, NullIfExpr *b)
392+
{
393+
COMPARE_SCALAR_FIELD(opno);
394+
/*
395+
* Special-case opfuncid: it is allowable for it to differ if one
396+
* node contains zero and the other doesn't. This just means that the
397+
* one node isn't as far along in the parse/plan pipeline and hasn't
398+
* had the opfuncid cache filled yet.
399+
*/
400+
if (a->opfuncid != b->opfuncid &&
401+
a->opfuncid != 0 &&
402+
b->opfuncid != 0)
403+
return false;
404+
405+
COMPARE_SCALAR_FIELD(opresulttype);
406+
COMPARE_SCALAR_FIELD(opretset);
407+
COMPARE_NODE_FIELD(args);
408+
409+
return true;
410+
}
411+
381412
static bool
382413
_equalNullTest(NullTest *a, NullTest *b)
383414
{
@@ -1613,6 +1644,12 @@ equal(void *a, void *b)
16131644
case T_CaseWhen:
16141645
retval = _equalCaseWhen(a, b);
16151646
break;
1647+
case T_CoalesceExpr:
1648+
retval = _equalCoalesceExpr(a, b);
1649+
break;
1650+
case T_NullIfExpr:
1651+
retval = _equalNullIfExpr(a, b);
1652+
break;
16161653
case T_NullTest:
16171654
retval = _equalNullTest(a, b);
16181655
break;

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