Implement READ_STRING_FIELD_NULL serializable read function.

When there is "" string, we need also to palloc memory in OidAssignment.

Authored-by: Zhang Wenchao zwcpostgres@gmail.com

src/backend/nodes/readfast.c

@@ -119,9 +119,26 @@
 		} \
 		var = nn;  }
 
+#define READ_STRING_VAR_NULL(var) \
+	{ int slen; char * nn = NULL; \
+		memcpy(&slen, read_str_ptr, sizeof(int)); \
+		read_str_ptr+=sizeof(int); \
+		if (slen>0) { \
+		    nn = palloc(slen+1); \
+		    memcpy(nn,read_str_ptr,slen); \
+		    read_str_ptr+=(slen); nn[slen]='\0'; \
+		} \
+		if (slen==0) { \
+			nn = palloc(1); \
+			nn[0] = '\0'; \
+		} \
+		var = nn;  }
+
 /* Read a character-string field */
 #define READ_STRING_FIELD(fldname)  READ_STRING_VAR(local_node->fldname)
 
+#define READ_STRING_FIELD_NULL(fldname)  READ_STRING_VAR_NULL(local_node->fldname)
+
 /* Read a parse location field (and throw away the value, per notes above) */
 #define READ_LOCATION_FIELD(fldname) READ_INT_FIELD(fldname)
 
@@ -892,7 +909,7 @@ _readOidAssignment(void)
 	READ_LOCALS(OidAssignment);
 
 	READ_OID_FIELD(catalog);
-	READ_STRING_FIELD(objname);
+	READ_STRING_FIELD_NULL(objname);
 	READ_OID_FIELD(namespaceOid);
 	READ_OID_FIELD(keyOid1);
 	READ_OID_FIELD(keyOid2);

src/test/regress/expected/gp_types.out

@@ -41,6 +41,7 @@ SELECT * FROM dml_bitvarying ORDER BY 1;
  00
 (1 row)
 
+CREATE TYPE size_t AS enum('');
 --
 -- Interval
 --
@@ -425,6 +426,7 @@ SELECT float8in(float8out(a)) FROM FLOATS ORDER BY a;
 COPY FLOATS TO '/tmp/floats';
 TRUNCATE FLOATS;
 COPY FLOATS FROM '/tmp/floats';
+DROP TYPE size_t;
 SELECT * FROM FLOATS ORDER BY a;
    a    
 --------

src/test/regress/sql/gp_types.sql

@@ -23,6 +23,8 @@ SELECT * FROM dml_bitvarying ORDER BY 1;
 UPDATE dml_bitvarying SET a = '000';
 SELECT * FROM dml_bitvarying ORDER BY 1;
 
+CREATE TYPE size_t AS enum('');
+
 --
 -- Interval
 --
@@ -172,4 +174,6 @@ COPY FLOATS TO '/tmp/floats';
 TRUNCATE FLOATS;
 COPY FLOATS FROM '/tmp/floats';
 
+DROP TYPE size_t;
+
 SELECT * FROM FLOATS ORDER BY a;