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>

3 files changed, 200 insertions, 15 deletions

diff --git a/src/backend/utils/adt/date.c b/src/backend/utils/adt/date.c
index 420f383a804..bc7d190210a 100644
--- a/src/backend/utils/adt/date.c
+++ b/src/backend/utils/adt/date.c
@@ -21,6 +21,7 @@
 #include <time.h>
 
 #include "access/hash.h"
+#include "access/xact.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
 #include "parser/scansup.h"
@@ -51,7 +52,6 @@ static void AdjustTimeForTypmod(TimeADT *time, int32 typmod);
 static int32
 anytime_typmodin(bool istz, ArrayType *ta)
 {
-	int32		typmod;
 	int32	   *tl;
 	int			n;
 
@@ -66,22 +66,27 @@ anytime_typmodin(bool istz, ArrayType *ta)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("invalid type modifier")));
 
-	if (*tl < 0)
+	return anytime_typmod_check(istz, tl[0]);
+}
+
+/* exported so parse_expr.c can use it */
+int32
+anytime_typmod_check(bool istz, int32 typmod)
+{
+	if (typmod < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("TIME(%d)%s precision must not be negative",
-						*tl, (istz ? " WITH TIME ZONE" : ""))));
-	if (*tl > MAX_TIME_PRECISION)
+						typmod, (istz ? " WITH TIME ZONE" : ""))));
+	if (typmod > MAX_TIME_PRECISION)
 	{
 		ereport(WARNING,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("TIME(%d)%s precision reduced to maximum allowed, %d",
-						*tl, (istz ? " WITH TIME ZONE" : ""),
+						typmod, (istz ? " WITH TIME ZONE" : ""),
 						MAX_TIME_PRECISION)));
 		typmod = MAX_TIME_PRECISION;
 	}
-	else
-		typmod = *tl;
 
 	return typmod;
 }
@@ -299,6 +304,80 @@ EncodeSpecialDate(DateADT dt, char *str)
 
 
 /*
+ * GetSQLCurrentDate -- implements CURRENT_DATE
+ */
+DateADT
+GetSQLCurrentDate(void)
+{
+	TimestampTz ts;
+	struct pg_tm tt,
+			   *tm = &tt;
+	fsec_t		fsec;
+	int			tz;
+
+	ts = GetCurrentTransactionStartTimestamp();
+
+	if (timestamp2tm(ts, &tz, tm, &fsec, NULL, NULL) != 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+				 errmsg("timestamp out of range")));
+
+	return date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - POSTGRES_EPOCH_JDATE;
+}
+
+/*
+ * GetSQLCurrentTime -- implements CURRENT_TIME, CURRENT_TIME(n)
+ */
+TimeTzADT *
+GetSQLCurrentTime(int32 typmod)
+{
+	TimeTzADT  *result;
+	TimestampTz ts;
+	struct pg_tm tt,
+			   *tm = &tt;
+	fsec_t		fsec;
+	int			tz;
+
+	ts = GetCurrentTransactionStartTimestamp();
+
+	if (timestamp2tm(ts, &tz, tm, &fsec, NULL, NULL) != 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+				 errmsg("timestamp out of range")));
+
+	result = (TimeTzADT *) palloc(sizeof(TimeTzADT));
+	tm2timetz(tm, fsec, tz, result);
+	AdjustTimeForTypmod(&(result->time), typmod);
+	return result;
+}
+
+/*
+ * GetSQLLocalTime -- implements LOCALTIME, LOCALTIME(n)
+ */
+TimeADT
+GetSQLLocalTime(int32 typmod)
+{
+	TimeADT		result;
+	TimestampTz ts;
+	struct pg_tm tt,
+			   *tm = &tt;
+	fsec_t		fsec;
+	int			tz;
+
+	ts = GetCurrentTransactionStartTimestamp();
+
+	if (timestamp2tm(ts, &tz, tm, &fsec, NULL, NULL) != 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+				 errmsg("timestamp out of range")));
+
+	tm2time(tm, fsec, &result);
+	AdjustTimeForTypmod(&result, typmod);
+	return result;
+}
+
+
+/*
  * Comparison functions for dates
  */
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index ec966c752ea..8a81d7a078f 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -6884,6 +6884,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 		case T_RowExpr:
 		case T_CoalesceExpr:
 		case T_MinMaxExpr:
+		case T_SQLValueFunction:
 		case T_XmlExpr:
 		case T_NullIfExpr:
 		case T_Aggref:
@@ -7871,6 +7872,67 @@ get_rule_expr(Node *node, deparse_context *context,
 			}
 			break;
 
+		case T_SQLValueFunction:
+			{
+				SQLValueFunction *svf = (SQLValueFunction *) node;
+
+				/*
+				 * Note: this code knows that typmod for time, timestamp, and
+				 * timestamptz just prints as integer.
+				 */
+				switch (svf->op)
+				{
+					case SVFOP_CURRENT_DATE:
+						appendStringInfoString(buf, "CURRENT_DATE");
+						break;
+					case SVFOP_CURRENT_TIME:
+						appendStringInfoString(buf, "CURRENT_TIME");
+						break;
+					case SVFOP_CURRENT_TIME_N:
+						appendStringInfo(buf, "CURRENT_TIME(%d)", svf->typmod);
+						break;
+					case SVFOP_CURRENT_TIMESTAMP:
+						appendStringInfoString(buf, "CURRENT_TIMESTAMP");
+						break;
+					case SVFOP_CURRENT_TIMESTAMP_N:
+						appendStringInfo(buf, "CURRENT_TIMESTAMP(%d)",
+										 svf->typmod);
+						break;
+					case SVFOP_LOCALTIME:
+						appendStringInfoString(buf, "LOCALTIME");
+						break;
+					case SVFOP_LOCALTIME_N:
+						appendStringInfo(buf, "LOCALTIME(%d)", svf->typmod);
+						break;
+					case SVFOP_LOCALTIMESTAMP:
+						appendStringInfoString(buf, "LOCALTIMESTAMP");
+						break;
+					case SVFOP_LOCALTIMESTAMP_N:
+						appendStringInfo(buf, "LOCALTIMESTAMP(%d)",
+										 svf->typmod);
+						break;
+					case SVFOP_CURRENT_ROLE:
+						appendStringInfoString(buf, "CURRENT_ROLE");
+						break;
+					case SVFOP_CURRENT_USER:
+						appendStringInfoString(buf, "CURRENT_USER");
+						break;
+					case SVFOP_USER:
+						appendStringInfoString(buf, "USER");
+						break;
+					case SVFOP_SESSION_USER:
+						appendStringInfoString(buf, "SESSION_USER");
+						break;
+					case SVFOP_CURRENT_CATALOG:
+						appendStringInfoString(buf, "CURRENT_CATALOG");
+						break;
+					case SVFOP_CURRENT_SCHEMA:
+						appendStringInfoString(buf, "CURRENT_SCHEMA");
+						break;
+				}
+			}
+			break;
+
 		case T_XmlExpr:
 			{
 				XmlExpr    *xexpr = (XmlExpr *) node;
diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index d7ee865cf75..c1d6f05b5ed 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -72,13 +72,13 @@ static Timestamp dt2local(Timestamp dt, int timezone);
 static void AdjustTimestampForTypmod(Timestamp *time, int32 typmod);
 static void AdjustIntervalForTypmod(Interval *interval, int32 typmod);
 static TimestampTz timestamp2timestamptz(Timestamp timestamp);
+static Timestamp timestamptz2timestamp(TimestampTz timestamp);
 
 
 /* common code for timestamptypmodin and timestamptztypmodin */
 static int32
 anytimestamp_typmodin(bool istz, ArrayType *ta)
 {
-	int32		typmod;
 	int32	   *tl;
 	int			n;
 
@@ -93,22 +93,27 @@ anytimestamp_typmodin(bool istz, ArrayType *ta)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("invalid type modifier")));
 
-	if (*tl < 0)
+	return anytimestamp_typmod_check(istz, tl[0]);
+}
+
+/* exported so parse_expr.c can use it */
+int32
+anytimestamp_typmod_check(bool istz, int32 typmod)
+{
+	if (typmod < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("TIMESTAMP(%d)%s precision must not be negative",
-						*tl, (istz ? " WITH TIME ZONE" : ""))));
-	if (*tl > MAX_TIMESTAMP_PRECISION)
+						typmod, (istz ? " WITH TIME ZONE" : ""))));
+	if (typmod > MAX_TIMESTAMP_PRECISION)
 	{
 		ereport(WARNING,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 		   errmsg("TIMESTAMP(%d)%s precision reduced to maximum allowed, %d",
-				  *tl, (istz ? " WITH TIME ZONE" : ""),
+				  typmod, (istz ? " WITH TIME ZONE" : ""),
 				  MAX_TIMESTAMP_PRECISION)));
 		typmod = MAX_TIMESTAMP_PRECISION;
 	}
-	else
-		typmod = *tl;
 
 	return typmod;
 }
@@ -336,6 +341,10 @@ timestamp_scale(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMP(result);
 }
 
+/*
+ * AdjustTimestampForTypmod --- round off a timestamp to suit given typmod
+ * Works for either timestamp or timestamptz.
+ */
 static void
 AdjustTimestampForTypmod(Timestamp *time, int32 typmod)
 {
@@ -1687,6 +1696,34 @@ IntegerTimestampToTimestampTz(int64 timestamp)
 #endif
 
 /*
+ * GetSQLCurrentTimestamp -- implements CURRENT_TIMESTAMP, CURRENT_TIMESTAMP(n)
+ */
+TimestampTz
+GetSQLCurrentTimestamp(int32 typmod)
+{
+	TimestampTz ts;
+
+	ts = GetCurrentTransactionStartTimestamp();
+	if (typmod >= 0)
+		AdjustTimestampForTypmod(&ts, typmod);
+	return ts;
+}
+
+/*
+ * GetSQLLocalTimestamp -- implements LOCALTIMESTAMP, LOCALTIMESTAMP(n)
+ */
+Timestamp
+GetSQLLocalTimestamp(int32 typmod)
+{
+	Timestamp	ts;
+
+	ts = timestamptz2timestamp(GetCurrentTransactionStartTimestamp());
+	if (typmod >= 0)
+		AdjustTimestampForTypmod(&ts, typmod);
+	return ts;
+}
+
+/*
  * TimestampDifference -- convert the difference between two timestamps
  *		into integer seconds and microseconds
  *
@@ -5415,6 +5452,13 @@ Datum
 timestamptz_timestamp(PG_FUNCTION_ARGS)
 {
 	TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
+
+	PG_RETURN_TIMESTAMP(timestamptz2timestamp(timestamp));
+}
+
+static Timestamp
+timestamptz2timestamp(TimestampTz timestamp)
+{
 	Timestamp	result;
 	struct pg_tm tt,
 			   *tm = &tt;
@@ -5434,7 +5478,7 @@ timestamptz_timestamp(PG_FUNCTION_ARGS)
 					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 					 errmsg("timestamp out of range")));
 	}
-	PG_RETURN_TIMESTAMP(result);
+	return result;
 }
 
 /* timestamptz_zone()