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Ensure an index that uses a whole-row Var still depends on its table.

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We failed to record any dependency on the underlying table for an index
declared like "create index i on t (foo(t.*))".  This would create trouble
if the table were dropped without previously dropping the index.  To fix,
simplify some overly-cute code in index_create(), accepting the possibility
that sometimes the whole-table dependency will be redundant.  Also document
this hazard in dependency.c.  Per report from Kevin Grittner.

In passing, prevent a core dump in pg_get_indexdef() if the index's table
can't be found.  I came across this while experimenting with Kevin's
example.  Not sure it's a real issue when the catalogs aren't corrupt, but
might as well be cautious.

Back-patch to all supported versions.
This commit is contained in:
Tom Lane 2010-11-02 17:15:07 -04:00
parent 35d5d962e1
commit 9f376e146b
3 changed files with 40 additions and 14 deletions
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15
src/backend/catalog/dependency.c
View File

@ -1238,6 +1238,12 @@ recordDependencyOnExpr(const ObjectAddress *depender,
* range table. An additional frammish is that dependencies on that
* relation (or its component columns) will be marked with 'self_behavior',
* whereas 'behavior' is used for everything else.
*
* NOTE: the caller should ensure that a whole-table dependency on the
* specified relation is created separately, if one is needed. In particular,
* a whole-row Var "relation.*" will not cause this routine to emit any
* dependency item. This is appropriate behavior for subexpressions of an
* ordinary query, so other cases need to cope as necessary.
*/
void
recordDependencyOnSingleRelExpr(const ObjectAddress *depender,
@ -1350,7 +1356,14 @@ find_expr_references_walker(Node *node,
/*
* A whole-row Var references no specific columns, so adds no new
* dependency.
* dependency. (We assume that there is a whole-table dependency
* arising from each underlying rangetable entry. While we could
* record such a dependency when finding a whole-row Var that
* references a relation directly, it's quite unclear how to extend
* that to whole-row Vars for JOINs, so it seems better to leave the
* responsibility with the range table. Note that this poses some
* risks for identifying dependencies of stand-alone expressions:
* whole-table references may need to be created separately.)
*/
if (var->varattno == InvalidAttrNumber)
return false;

15
src/backend/catalog/index.c
View File

@ -50,7 +50,6 @@
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/var.h"
#include "parser/parser.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
@ -858,16 +857,12 @@ index_create(Oid heapRelationId,
}
/*
* It's possible for an index to not depend on any columns of the
* table at all, in which case we need to give it a dependency on
* the table as a whole; else it won't get dropped when the table
* is dropped. This edge case is not totally useless; for
* example, a unique index on a constant expression can serve to
* prevent a table from containing more than one row.
* If there are no simply-referenced columns, give the index an
* auto dependency on the whole table. In most cases, this will
* be redundant, but it might not be if the index expressions and
* predicate contain no Vars or only whole-row Vars.
*/
if (!have_simple_col &&
!contain_vars_of_level((Node *) indexInfo->ii_Expressions, 0) &&
!contain_vars_of_level((Node *) indexInfo->ii_Predicate, 0))
if (!have_simple_col)
{
referenced.classId = RelationRelationId;
referenced.objectId = heapRelationId;

24
src/backend/utils/adt/ruleutils.c
View File

@ -240,6 +240,7 @@ static void get_opclass_name(Oid opclass, Oid actual_datatype,
static Node *processIndirection(Node *node, deparse_context *context,
bool printit);
static void printSubscripts(ArrayRef *aref, deparse_context *context);
static char *get_relation_name(Oid relid);
static char *generate_relation_name(Oid relid, List *namespaces);
static char *generate_function_name(Oid funcid, int nargs, List *argnames,
Oid *argtypes, bool *is_variadic);
@ -857,7 +858,7 @@ pg_get_indexdef_worker(Oid indexrelid, int colno,
indexpr_item = list_head(indexprs);
context = deparse_context_for(get_rel_name(indrelid), indrelid);
context = deparse_context_for(get_relation_name(indrelid), indrelid);
/*
* Start the index definition. Note that the index's name should never be
@ -1261,7 +1262,7 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
if (conForm->conrelid != InvalidOid)
{
/* relation constraint */
context = deparse_context_for(get_rel_name(conForm->conrelid),
context = deparse_context_for(get_relation_name(conForm->conrelid),
conForm->conrelid);
}
else
@ -6314,7 +6315,7 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
gavealias = true;
}
else if (rte->rtekind == RTE_RELATION &&
strcmp(rte->eref->aliasname, get_rel_name(rte->relid)) != 0)
strcmp(rte->eref->aliasname, get_relation_name(rte->relid)) != 0)
{
/*
* Apparently the rel has been renamed since the rule was made.
@ -6817,6 +6818,23 @@ quote_qualified_identifier(const char *qualifier,
return buf.data;
}
/*
* get_relation_name
* Get the unqualified name of a relation specified by OID
*
* This differs from the underlying get_rel_name() function in that it will
* throw error instead of silently returning NULL if the OID is bad.
*/
static char *
get_relation_name(Oid relid)
{
char *relname = get_rel_name(relid);
if (!relname)
elog(ERROR, "cache lookup failed for relation %u", relid);
return relname;
}
/*
* generate_relation_name
* Compute the name to display for a relation specified by OID