/*
* Get the catalog entry for an exttable relation (from pg_exttable)
*/
ExtTableEntry*
GetExtTableEntry(Oid relid)
{
ExtTableEntry *extentry;
extentry = GetExtTableEntryIfExists(relid);
if (!extentry)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("missing pg_exttable entry for relation \"%s\"",
get_rel_name(relid))));
return extentry;
}
/*
* GpPolicyFetch
*
* Looks up the distribution policy of given relation from
* gp_distribution_policy table (or by implicit rules for external tables)
* Returns an GpPolicy object, allocated in the specified context, containing
* the information.
*
* The caller is responsible for passing in a valid relation oid. This
* function does not check, and assigns a policy of type POLICYTYPE_ENTRY
* for any oid not found in gp_distribution_policy.
*/
GpPolicy *
GpPolicyFetch(MemoryContext mcxt, Oid tbloid)
{
GpPolicy *policy = NULL; /* The result */
Relation gp_policy_rel;
cqContext cqc;
HeapTuple gp_policy_tuple = NULL;
/*
* Skip if qExec or utility mode.
*/
if (Gp_role != GP_ROLE_DISPATCH)
{
policy = (GpPolicy *) MemoryContextAlloc(mcxt, SizeOfGpPolicy(0));
policy->ptype = POLICYTYPE_ENTRY;
policy->nattrs = 0;
return policy;
}
/*
* EXECUTE-type external tables have an "ON ..." specification, stored
* in pg_exttable.location. See if it's "MASTER_ONLY". Other types of
* external tables have a gp_distribution_policy row, like normal tables.
*/
if (get_rel_relstorage(tbloid) == RELSTORAGE_EXTERNAL)
{
/*
* An external table really should have a pg_exttable entry, but
* there's currently a transient state during creation of an external
* table, where the pg_class entry has been created, and its loaded
* into the relcache, before the pg_exttable entry has been created.
* Silently ignore missing pg_exttable rows to cope with that.
*/
ExtTableEntry *e = GetExtTableEntryIfExists(tbloid);
/*
* Writeable external tables have gp_distribution_policy entries,
* like regular tables. Readable external tables are implicitly
* randomly distributed, except for "EXECUTE ... ON MASTER" ones.
*/
if (e && !e->iswritable)
{
if (e->command)
{
char *on_clause = (char *) strVal(linitial(e->locations));
if (strcmp(on_clause, "MASTER_ONLY") == 0)
{
policy = (GpPolicy *) MemoryContextAlloc(mcxt, SizeOfGpPolicy(0));
policy->ptype = POLICYTYPE_ENTRY;
policy->nattrs = 0;
return policy;
}
}
policy = (GpPolicy *) MemoryContextAlloc(mcxt, SizeOfGpPolicy(0));
policy->ptype = POLICYTYPE_PARTITIONED;
policy->nattrs = 0;
return policy;
}
}
/*
* We need to read the gp_distribution_policy table
*/
gp_policy_rel = heap_open(GpPolicyRelationId, AccessShareLock);
/*
* Select by value of the localoid field
*/
gp_policy_tuple = caql_getfirst(
caql_addrel(cqclr(&cqc), gp_policy_rel),
cql("SELECT * FROM gp_distribution_policy "
" WHERE localoid = :1 ",
ObjectIdGetDatum(tbloid)));
/*
* Read first (and only) tuple
*/
if (HeapTupleIsValid(gp_policy_tuple))
{
bool isNull;
Datum attr;
int i,
nattrs = 0;
int16 *attrnums = NULL;
/*
* Get the attributes on which to partition.
*/
attr = heap_getattr(gp_policy_tuple, Anum_gp_policy_attrnums,
RelationGetDescr(gp_policy_rel), &isNull);
/*
* Get distribution keys only if this table has a policy.
*/
if(!isNull)
{
extract_INT2OID_array(attr, &nattrs, &attrnums);
Assert(nattrs >= 0);
}
/* Create an GpPolicy object. */
policy = (GpPolicy *) MemoryContextAlloc(mcxt, SizeOfGpPolicy(nattrs));
policy->ptype = POLICYTYPE_PARTITIONED;
policy->nattrs = nattrs;
for (i = 0; i < nattrs; i++)
{
policy->attrs[i] = attrnums[i];
}
}
/*
* Cleanup the scan and relation objects.
*/
heap_close(gp_policy_rel, AccessShareLock);
/* Interpret absence of a valid policy row as POLICYTYPE_ENTRY */
if (policy == NULL)
{
policy = (GpPolicy *) MemoryContextAlloc(mcxt, SizeOfGpPolicy(0));
policy->ptype = POLICYTYPE_ENTRY;
policy->nattrs = 0;
}
return policy;
} /* GpPolicyFetch */