Fix parsetree representation of XMLTABLE(XMLNAMESPACES(DEFAULT ...)).

tglsfdc · tglsfdc · commit a552e3bc502e · 2018-09-17T13:16:32.000-04:00
The original coding for XMLTABLE thought it could represent a default namespace by a T_String Value node with a null string pointer. That's not okay, though; in particular outfuncs.c/readfuncs.c are not on board with such a representation, meaning you'll get a null pointer crash if you try to store a view or rule containing this construct. To fix, change the parsetree representation so that we have a NULL list element, instead of a bogus Value node. This isn't really a functional limitation since default XML namespaces aren't yet implemented in the executor; you'd just get "DEFAULT namespace is not supported" anyway. But crashes are not nice, so back-patch to v10 where this syntax was added. Ordinarily we'd consider a parsetree representation change to be un-backpatchable; but since existing releases would crash on the way to storing such constructs, there can't be any existing views/rules to be incompatible with. Per report from Andrey Lepikhov. Discussion: https://postgr.es/m/3690074f-abd2-56a9-144a-aa5545d7a291@postgrespro.ru
diff --git a/src/backend/executor/nodeTableFuncscan.c b/src/backend/executor/nodeTableFuncscan.c
@@ -370,8 +370,9 @@ tfuncInitialize(TableFuncScanState *tstate, ExprContext *econtext, Datum doc)
 	forboth(lc1, tstate->ns_uris, lc2, tstate->ns_names)
 	{
 		ExprState  *expr = (ExprState *) lfirst(lc1);
-		char	   *ns_name = strVal(lfirst(lc2));
+		Value	   *ns_node = (Value *) lfirst(lc2);
 		char	   *ns_uri;
+		char	   *ns_name;
 
 		value = ExecEvalExpr((ExprState *) expr, econtext, &isnull);
 		if (isnull)
@@ -380,6 +381,9 @@ tfuncInitialize(TableFuncScanState *tstate, ExprContext *econtext, Datum doc)
 					 errmsg("namespace URI must not be null")));
 		ns_uri = TextDatumGetCString(value);
 
+		/* DEFAULT is passed down to SetNamespace as NULL */
+		ns_name = ns_node ? strVal(ns_node) : NULL;
+
 		routine->SetNamespace(tstate, ns_name, ns_uri);
 	}
 
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
@@ -772,7 +772,7 @@ transformRangeTableFunc(ParseState *pstate, RangeTableFunc *rtf)
 	/* undef ordinality column number */
 	tf->ordinalitycol = -1;
 
-
+	/* Process column specs */
 	names = palloc(sizeof(char *) * list_length(rtf->columns));
 
 	colno = 0;
@@ -893,15 +893,15 @@ transformRangeTableFunc(ParseState *pstate, RangeTableFunc *rtf)
 			{
 				foreach(lc2, ns_names)
 				{
-					char	   *name = strVal(lfirst(lc2));
+					Value	   *ns_node = (Value *) lfirst(lc2);
 
-					if (name == NULL)
+					if (ns_node == NULL)
 						continue;
-					if (strcmp(name, r->name) == 0)
+					if (strcmp(strVal(ns_node), r->name) == 0)
 						ereport(ERROR,
 								(errcode(ERRCODE_SYNTAX_ERROR),
 								 errmsg("namespace name \"%s\" is not unique",
-										name),
+										r->name),
 								 parser_errposition(pstate, r->location)));
 				}
 			}
@@ -915,8 +915,9 @@ transformRangeTableFunc(ParseState *pstate, RangeTableFunc *rtf)
 				default_ns_seen = true;
 			}
 
-			/* Note the string may be NULL */
-			ns_names = lappend(ns_names, makeString(r->name));
+			/* We represent DEFAULT by a null pointer */
+			ns_names = lappend(ns_names,
+							   r->name ? makeString(r->name) : NULL);
 		}
 
 		tf->ns_uris = ns_uris;
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
@@ -9618,17 +9618,17 @@ get_tablefunc(TableFunc *tf, deparse_context *context, bool showimplicit)
 		forboth(lc1, tf->ns_uris, lc2, tf->ns_names)
 		{
 			Node	   *expr = (Node *) lfirst(lc1);
-			char	   *name = strVal(lfirst(lc2));
+			Value	   *ns_node = (Value *) lfirst(lc2);
 
 			if (!first)
 				appendStringInfoString(buf, ", ");
 			else
 				first = false;
 
-			if (name != NULL)
+			if (ns_node != NULL)
 			{
 				get_rule_expr(expr, context, showimplicit);
-				appendStringInfo(buf, " AS %s", name);
+				appendStringInfo(buf, " AS %s", strVal(ns_node));
 			}
 			else
 			{
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
@@ -1476,8 +1476,8 @@ typedef struct TableFuncScanState
 	ExprState  *rowexpr;		/* state for row-generating expression */
 	List	   *colexprs;		/* state for column-generating expression */
 	List	   *coldefexprs;	/* state for column default expressions */
-	List	   *ns_names;		/* list of str nodes with namespace names */
-	List	   *ns_uris;		/* list of states of namespace uri exprs */
+	List	   *ns_names;		/* same as TableFunc.ns_names */
+	List	   *ns_uris;		/* list of states of namespace URI exprs */
 	Bitmapset  *notnulls;		/* nullability flag for each output column */
 	void	   *opaque;			/* table builder private space */
 	const struct TableFuncRoutine *routine; /* table builder methods */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
@@ -75,12 +75,15 @@ typedef struct RangeVar
 
 /*
  * TableFunc - node for a table function, such as XMLTABLE.
+ *
+ * Entries in the ns_names list are either string Value nodes containing
+ * literal namespace names, or NULL pointers to represent DEFAULT.
  */
 typedef struct TableFunc
 {
 	NodeTag		type;
-	List	   *ns_uris;		/* list of namespace uri */
-	List	   *ns_names;		/* list of namespace names */
+	List	   *ns_uris;		/* list of namespace URI expressions */
+	List	   *ns_names;		/* list of namespace names or NULL */
 	Node	   *docexpr;		/* input document expression */
 	Node	   *rowexpr;		/* row filter expression */
 	List	   *colnames;		/* column names (list of String) */

Original file line number	Diff line number	Diff line change
`@@ -772,7 +772,7 @@ transformRangeTableFunc(ParseState pstate, RangeTableFunc rtf)`
`772`	`772`	`/* undef ordinality column number */`
`773`	`773`	`tf->ordinalitycol = -1;`
`774`	`774`
`775`		`-`
	`775`	`+ /* Process column specs */`
`776`	`776`	`names = palloc(sizeof(char ) list_length(rtf->columns));`
`777`	`777`
`778`	`778`	`colno = 0;`
`@@ -893,15 +893,15 @@ transformRangeTableFunc(ParseState pstate, RangeTableFunc rtf)`
`893`	`893`	`{`
`894`	`894`	`foreach(lc2, ns_names)`
`895`	`895`	`{`
`896`		`- char *name = strVal(lfirst(lc2));`
	`896`	`+ Value ns_node = (Value ) lfirst(lc2);`
`897`	`897`
`898`		`- if (name == NULL)`
	`898`	`+ if (ns_node == NULL)`
`899`	`899`	`continue;`
`900`		`- if (strcmp(name, r->name) == 0)`
	`900`	`+ if (strcmp(strVal(ns_node), r->name) == 0)`
`901`	`901`	`ereport(ERROR,`
`902`	`902`	`(errcode(ERRCODE_SYNTAX_ERROR),`
`903`	`903`	`errmsg("namespace name \"%s\" is not unique",`
`904`		`- name),`
	`904`	`+ r->name),`
`905`	`905`	`parser_errposition(pstate, r->location)));`
`906`	`906`	`}`
`907`	`907`	`}`
`@@ -915,8 +915,9 @@ transformRangeTableFunc(ParseState pstate, RangeTableFunc rtf)`
`915`	`915`	`default_ns_seen = true;`
`916`	`916`	`}`
`917`	`917`
`918`		`- /* Note the string may be NULL */`
`919`		`- ns_names = lappend(ns_names, makeString(r->name));`
	`918`	`+ /* We represent DEFAULT by a null pointer */`
	`919`	`+ ns_names = lappend(ns_names,`
	`920`	`+ r->name ? makeString(r->name) : NULL);`
`920`	`921`	`}`
`921`	`922`
`922`	`923`	`tf->ns_uris = ns_uris;`
Original file line number	Diff line number	Diff line change
`@@ -9618,17 +9618,17 @@ get_tablefunc(TableFunc tf, deparse_context context, bool showimplicit)`
`9618`	`9618`	`forboth(lc1, tf->ns_uris, lc2, tf->ns_names)`
`9619`	`9619`	`{`
`9620`	`9620`	`Node expr = (Node ) lfirst(lc1);`
`9621`		`- char *name = strVal(lfirst(lc2));`
	`9621`	`+ Value ns_node = (Value ) lfirst(lc2);`
`9622`	`9622`
`9623`	`9623`	`if (!first)`
`9624`	`9624`	`appendStringInfoString(buf, ", ");`
`9625`	`9625`	`else`
`9626`	`9626`	`first = false;`
`9627`	`9627`
`9628`		`- if (name != NULL)`
	`9628`	`+ if (ns_node != NULL)`
`9629`	`9629`	`{`
`9630`	`9630`	`get_rule_expr(expr, context, showimplicit);`
`9631`		`- appendStringInfo(buf, " AS %s", name);`
	`9631`	`+ appendStringInfo(buf, " AS %s", strVal(ns_node));`
`9632`	`9632`	`}`
`9633`	`9633`	`else`
`9634`	`9634`	`{`