From 0bb51aa96783e8a6c473c2b5e3725e23e95db834 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 16 Aug 2016 20:33:01 -0400
Subject: Improve parsetree representation of special functions such as
 CURRENT_DATE.

We implement a dozen or so parameterless functions that the SQL standard
defines special syntax for.  Up to now, that was done by converting them
into more or less ad-hoc constructs such as "'now'::text::date".  That's
messy for multiple reasons: it exposes what should be implementation
details to users, and performance is worse than it needs to be in several
cases.  To improve matters, invent a new expression node type
SQLValueFunction that can represent any of these parameterless functions.

Bump catversion because this changes stored parsetrees for rules.

Discussion: <30058.1463091294@sss.pgh.pa.us>
---
 src/backend/parser/parse_expr.c | 62 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

(limited to 'src/backend/parser/parse_expr.c')

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index cead21283d0..63f7965532e 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -34,7 +34,9 @@
 #include "parser/parse_type.h"
 #include "parser/parse_agg.h"
 #include "utils/builtins.h"
+#include "utils/date.h"
 #include "utils/lsyscache.h"
+#include "utils/timestamp.h"
 #include "utils/xml.h"
 
 
@@ -107,6 +109,8 @@ static Node *transformArrayExpr(ParseState *pstate, A_ArrayExpr *a,
 static Node *transformRowExpr(ParseState *pstate, RowExpr *r);
 static Node *transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c);
 static Node *transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m);
+static Node *transformSQLValueFunction(ParseState *pstate,
+						  SQLValueFunction *svf);
 static Node *transformXmlExpr(ParseState *pstate, XmlExpr *x);
 static Node *transformXmlSerialize(ParseState *pstate, XmlSerialize *xs);
 static Node *transformBooleanTest(ParseState *pstate, BooleanTest *b);
@@ -306,6 +310,11 @@ transformExprRecurse(ParseState *pstate, Node *expr)
 			result = transformMinMaxExpr(pstate, (MinMaxExpr *) expr);
 			break;
 
+		case T_SQLValueFunction:
+			result = transformSQLValueFunction(pstate,
+											   (SQLValueFunction *) expr);
+			break;
+
 		case T_XmlExpr:
 			result = transformXmlExpr(pstate, (XmlExpr *) expr);
 			break;
@@ -2178,6 +2187,59 @@ transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m)
 	return (Node *) newm;
 }
 
+static Node *
+transformSQLValueFunction(ParseState *pstate, SQLValueFunction *svf)
+{
+	/*
+	 * All we need to do is insert the correct result type and (where needed)
+	 * validate the typmod, so we just modify the node in-place.
+	 */
+	switch (svf->op)
+	{
+		case SVFOP_CURRENT_DATE:
+			svf->type = DATEOID;
+			break;
+		case SVFOP_CURRENT_TIME:
+			svf->type = TIMETZOID;
+			break;
+		case SVFOP_CURRENT_TIME_N:
+			svf->type = TIMETZOID;
+			svf->typmod = anytime_typmod_check(true, svf->typmod);
+			break;
+		case SVFOP_CURRENT_TIMESTAMP:
+			svf->type = TIMESTAMPTZOID;
+			break;
+		case SVFOP_CURRENT_TIMESTAMP_N:
+			svf->type = TIMESTAMPTZOID;
+			svf->typmod = anytimestamp_typmod_check(true, svf->typmod);
+			break;
+		case SVFOP_LOCALTIME:
+			svf->type = TIMEOID;
+			break;
+		case SVFOP_LOCALTIME_N:
+			svf->type = TIMEOID;
+			svf->typmod = anytime_typmod_check(false, svf->typmod);
+			break;
+		case SVFOP_LOCALTIMESTAMP:
+			svf->type = TIMESTAMPOID;
+			break;
+		case SVFOP_LOCALTIMESTAMP_N:
+			svf->type = TIMESTAMPOID;
+			svf->typmod = anytimestamp_typmod_check(false, svf->typmod);
+			break;
+		case SVFOP_CURRENT_ROLE:
+		case SVFOP_CURRENT_USER:
+		case SVFOP_USER:
+		case SVFOP_SESSION_USER:
+		case SVFOP_CURRENT_CATALOG:
+		case SVFOP_CURRENT_SCHEMA:
+			svf->type = NAMEOID;
+			break;
+	}
+
+	return (Node *) svf;
+}
+
 static Node *
 transformXmlExpr(ParseState *pstate, XmlExpr *x)
 {
-- 
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