Support empty string handling for date and time datatypes

Add TSQL-compatible handling of empty string ('') for date and time
types, defaulting to '1900-01-01' for date and '00:00:00.0000000' for
time, similar to datetime, datetime2, datetimeoffset, smalldatetime.

Task: BABEL-3433
Signed-off-by: Manisha Deshpande <[email protected]>

Author: manisha-deshpande

src/backend/utils/adt/date.c

@@ -29,6 +29,7 @@
 #include "miscadmin.h"
 #include "nodes/supportnodes.h"
 #include "parser/scansup.h"
+#include "parser/parser.h"
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/date.h"
@@ -127,6 +128,19 @@ date_in(PG_FUNCTION_ARGS)
 	char		workbuf[MAXDATELEN + 1];
 	DateTimeErrorExtra extra;
 
+	/*
+	 * Set input to default '1900-01-01' if empty string encountered
+	 */
+	if ((*str == '\0') && (sql_dialect == SQL_DIALECT_TSQL))
+	{
+		tm->tm_year = 1900;
+		tm->tm_mon = 1;
+		tm->tm_mday = 1;
+
+		date = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - POSTGRES_EPOCH_JDATE;
+		PG_RETURN_DATEADT(date);
+	}
+
 	dterr = ParseDateTime(str, workbuf, sizeof(workbuf),
 						  field, ftype, MAXDATEFIELDS, &nf);
 	if (dterr == 0)
@@ -1392,6 +1406,17 @@ time_in(PG_FUNCTION_ARGS)
 	int			ftype[MAXDATEFIELDS];
 	DateTimeErrorExtra extra;
 
+	/*
+	 * Set input to default '00:00:00.0000000' if empty string encountered
+	 */
+	if ((*str == '\0') && (sql_dialect == SQL_DIALECT_TSQL))
+	{
+		tm->tm_hour = tm->tm_min = tm->tm_sec = 0;
+		tm2time(tm, 0, &result);
+		AdjustTimeForTypmod(&result, typmod);
+		PG_RETURN_TIMEADT(result);
+	}
+
 	dterr = ParseDateTime(str, workbuf, sizeof(workbuf),
 						  field, ftype, MAXDATEFIELDS, &nf);
 	if (dterr == 0)