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Harden tableam against nonexistant / wrong kind of AMs.

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Previously it was allowed to set default_table_access_method to an
empty string. That makes sense for default_tablespace, where that was
copied from, as it signals falling back to the database's default
tablespace. As there is no equivalent for table AMs, forbid that.

Also make sure to throw a usable error when creating a table using an
index AM, by using get_am_type_oid() to implement get_table_am_oid()
instead of a separate copy. Previously we'd error out only later, in
GetTableAmRoutine().

Thirdly remove GetTableAmRoutineByAmId() - it was only used in an
earlier version of 8586bf7ed8.

Add tests for the above (some for index AMs as well).
This commit is contained in:
Andres Freund
2019-04-04 17:17:50 -07:00
parent 344b7e11bb
commit ea97e440b8
9 changed files with 119 additions and 110 deletions
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110
src/backend/access/table/tableamapi.c
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@ -17,14 +17,12 @@
#include "access/xact.h"
#include "catalog/pg_am.h"
#include "catalog/pg_proc.h"
#include "commands/defrem.h"
#include "utils/fmgroids.h"
#include "utils/memutils.h"
#include "utils/syscache.h"
static Oid get_table_am_oid(const char *tableamname, bool missing_ok);
/*
* GetTableAmRoutine
* Call the specified access method handler routine to get its
@ -41,7 +39,7 @@ GetTableAmRoutine(Oid amhandler)
routine = (TableAmRoutine *) DatumGetPointer(datum);
if (routine == NULL || !IsA(routine, TableAmRoutine))
elog(ERROR, "Table access method handler %u did not return a TableAmRoutine struct",
elog(ERROR, "table access method handler %u did not return a TableAmRoutine struct",
amhandler);
/*
@ -98,106 +96,30 @@ GetTableAmRoutine(Oid amhandler)
return routine;
}
/*
* GetTableAmRoutineByAmId - look up the handler of the table access
* method with the given OID, and get its TableAmRoutine struct.
*/
const TableAmRoutine *
GetTableAmRoutineByAmId(Oid amoid)
{
regproc amhandler;
HeapTuple tuple;
Form_pg_am amform;
/* Get handler function OID for the access method */
tuple = SearchSysCache1(AMOID, ObjectIdGetDatum(amoid));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for access method %u",
amoid);
amform = (Form_pg_am) GETSTRUCT(tuple);
/* Check that it is a table access method */
if (amform->amtype != AMTYPE_TABLE)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("access method \"%s\" is not of type %s",
NameStr(amform->amname), "TABLE")));
amhandler = amform->amhandler;
/* Complain if handler OID is invalid */
if (!RegProcedureIsValid(amhandler))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("table access method \"%s\" does not have a handler",
NameStr(amform->amname))));
ReleaseSysCache(tuple);
/* And finally, call the handler function to get the API struct. */
return GetTableAmRoutine(amhandler);
}
/*
* get_table_am_oid - given a table access method name, look up the OID
*
* If missing_ok is false, throw an error if table access method name not
* found. If true, just return InvalidOid.
*/
static Oid
get_table_am_oid(const char *tableamname, bool missing_ok)
{
Oid result;
Relation rel;
TableScanDesc scandesc;
HeapTuple tuple;
ScanKeyData entry[1];
/*
* Search pg_am. We use a heapscan here even though there is an index on
* name, on the theory that pg_am will usually have just a few entries and
* so an indexed lookup is a waste of effort.
*/
rel = heap_open(AccessMethodRelationId, AccessShareLock);
ScanKeyInit(&entry[0],
Anum_pg_am_amname,
BTEqualStrategyNumber, F_NAMEEQ,
CStringGetDatum(tableamname));
scandesc = table_beginscan_catalog(rel, 1, entry);
tuple = heap_getnext(scandesc, ForwardScanDirection);
/* We assume that there can be at most one matching tuple */
if (HeapTupleIsValid(tuple) &&
((Form_pg_am) GETSTRUCT(tuple))->amtype == AMTYPE_TABLE)
result = ((Form_pg_am) GETSTRUCT(tuple))->oid;
else
result = InvalidOid;
table_endscan(scandesc);
heap_close(rel, AccessShareLock);
if (!OidIsValid(result) && !missing_ok)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("table access method \"%s\" does not exist",
tableamname)));
return result;
}
/* check_hook: validate new default_table_access_method */
bool
check_default_table_access_method(char **newval, void **extra, GucSource source)
{
if (**newval == '\0')
{
GUC_check_errdetail("default_table_access_method may not be empty.");
return false;
}
if (strlen(*newval) >= NAMEDATALEN)
{
GUC_check_errdetail("default_table_access_method is too long (maximum %d characters).",
NAMEDATALEN - 1);
return false;
}
/*
* If we aren't inside a transaction, we cannot do database access so
* cannot verify the name. Must accept the value on faith.
*/
if (IsTransactionState())
{
if (**newval != '\0' &&
!OidIsValid(get_table_am_oid(*newval, true)))
if (!OidIsValid(get_table_am_oid(*newval, true)))
{
/*
* When source == PGC_S_TEST, don't throw a hard error for a