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

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
index abbf0e4d445a7795a71a8b852f6bfd96b32ff868..a9fd3fda6be67f050ff69064e9087a52feec9f29 100644 (file)
--- a/src/backend/executor/nodeTableFuncscan.c
+++ b/src/backend/executor/nodeTableFuncscan.c
@@ -364,8 +364,9 @@ 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)
@@ -374,6 +375,9 @@ 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
index cfd4b91897f43d4f64a2c725016c7b5fa72b7bf5..d6b93f55dfd51c192206e5f17610a097ec492f65 100644 (file)
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -779,7 +779,7 @@ 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;
@@ -900,15 +900,15 @@ 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)));
                }
            }
@@ -922,8 +922,9 @@ 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
index 4c2408d655135c020cab57e580184bae8200697c..eecd64e4b57266d66524d4030cf119f5a898bb4f 100644 (file)
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9739,17 +9739,17 @@ 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
index c830f141b1682ad743f7cb33e90d080963f90c8c..687d7cd2f41afa182fe175b8bdd386ff80d6a36e 100644 (file)
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1573,8 +1573,8 @@ 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
index 1b4b0d75afa042a44930773cfe66ea347f1c69ef..40f6eb03d241f795d716f78732cd1d8f49aa1ee4 100644 (file)
--- 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) */