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

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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
This commit is contained in:
Tom Lane
2018-09-17 13:16:32 -04:00
parent 789ba5029a
commit 07a3af0ff8
5 changed files with 23 additions and 15 deletions
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6
src/backend/executor/nodeTableFuncscan.c
View File

@ -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);
}