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Disallow LATERAL references to the target table of an UPDATE/DELETE.

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On second thought, commit 0c051c9008 was
over-hasty: rather than allowing this case, we ought to reject it for now.
That leaves the field clear for a future feature that allows the target
table to be re-specified in the FROM (or USING) clause, which will enable
left-joining the target table to something else.  We can then also allow
LATERAL references to such an explicitly re-specified target table.
But allowing them right now will create ambiguities or worse for such a
feature, and it isn't something we documented 9.3 as supporting.

While at it, add a convenience subroutine to avoid having several copies
of the ereport for disalllowed-LATERAL-reference cases.
This commit is contained in:
Tom Lane
2014-01-11 19:03:12 -05:00
parent 910bac5953
commit 158b7fa6a3
5 changed files with 72 additions and 66 deletions
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62
src/backend/parser/parse_relation.c
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@ -37,6 +37,8 @@ static RangeTblEntry *scanNameSpaceForRefname(ParseState *pstate,
const char *refname, int location);
static RangeTblEntry *scanNameSpaceForRelid(ParseState *pstate, Oid relid,
int location);
static void check_lateral_ref_ok(ParseState *pstate, ParseNamespaceItem *nsitem,
int location);
static void markRTEForSelectPriv(ParseState *pstate, RangeTblEntry *rte,
int rtindex, AttrNumber col);
static void expandRelation(Oid relid, Alias *eref,
@ -170,14 +172,7 @@ scanNameSpaceForRefname(ParseState *pstate, const char *refname, int location)
errmsg("table reference \"%s\" is ambiguous",
refname),
parser_errposition(pstate, location)));
/* SQL:2008 demands this be an error, not an invisible item */
if (nsitem->p_lateral_only && !nsitem->p_lateral_ok)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
errmsg("invalid reference to FROM-clause entry for table \"%s\"",
refname),
errdetail("The combining JOIN type must be INNER or LEFT for a LATERAL reference."),
parser_errposition(pstate, location)));
check_lateral_ref_ok(pstate, nsitem, location);
result = rte;
}
}
@ -221,14 +216,7 @@ scanNameSpaceForRelid(ParseState *pstate, Oid relid, int location)
errmsg("table reference %u is ambiguous",
relid),
parser_errposition(pstate, location)));
/* SQL:2008 demands this be an error, not an invisible item */
if (nsitem->p_lateral_only && !nsitem->p_lateral_ok)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
errmsg("invalid reference to FROM-clause entry for table \"%s\"",
rte->eref->aliasname),
errdetail("The combining JOIN type must be INNER or LEFT for a LATERAL reference."),
parser_errposition(pstate, location)));
check_lateral_ref_ok(pstate, nsitem, location);
result = rte;
}
}
@ -410,6 +398,37 @@ checkNameSpaceConflicts(ParseState *pstate, List *namespace1,
}
}
/*
* Complain if a namespace item is currently disallowed as a LATERAL reference.
* This enforces both SQL:2008's rather odd idea of what to do with a LATERAL
* reference to the wrong side of an outer join, and our own prohibition on
* referencing the target table of an UPDATE or DELETE as a lateral reference
* in a FROM/USING clause.
*
* Convenience subroutine to avoid multiple copies of a rather ugly ereport.
*/
static void
check_lateral_ref_ok(ParseState *pstate, ParseNamespaceItem *nsitem,
int location)
{
if (nsitem->p_lateral_only && !nsitem->p_lateral_ok)
{
/* SQL:2008 demands this be an error, not an invisible item */
RangeTblEntry *rte = nsitem->p_rte;
char *refname = rte->eref->aliasname;
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
errmsg("invalid reference to FROM-clause entry for table \"%s\"",
refname),
(rte == pstate->p_target_rangetblentry) ?
errhint("There is an entry for table \"%s\", but it cannot be referenced from this part of the query.",
refname) :
errdetail("The combining JOIN type must be INNER or LEFT for a LATERAL reference."),
parser_errposition(pstate, location)));
}
}
/*
* given an RTE, return RT index (starting with 1) of the entry,
* and optionally get its nesting depth (0 = current). If sublevels_up
@ -632,15 +651,8 @@ colNameToVar(ParseState *pstate, char *colname, bool localonly,
(errcode(ERRCODE_AMBIGUOUS_COLUMN),
errmsg("column reference \"%s\" is ambiguous",
colname),
parser_errposition(orig_pstate, location)));
/* SQL:2008 demands this be an error, not an invisible item */
if (nsitem->p_lateral_only && !nsitem->p_lateral_ok)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
errmsg("invalid reference to FROM-clause entry for table \"%s\"",
rte->eref->aliasname),
errdetail("The combining JOIN type must be INNER or LEFT for a LATERAL reference."),
parser_errposition(orig_pstate, location)));
parser_errposition(pstate, location)));
check_lateral_ref_ok(pstate, nsitem, location);
result = newresult;
}
}