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Add SQL-accessible functions for inspecting index AM properties.

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Per discussion, we should provide such functions to replace the lost
ability to discover AM properties by inspecting pg_am (cf commit
65c5fcd35).  The added functionality is also meant to displace any code
that was looking directly at pg_index.indoption, since we'd rather not
believe that the bit meanings in that field are part of any client API
contract.

As future-proofing, define the SQL API to not assume that properties that
are currently AM-wide or index-wide will remain so unless they logically
must be; instead, expose them only when inquiring about a specific index
or even specific index column.  Also provide the ability for an index
AM to override the behavior.

In passing, document pg_am.amtype, overlooked in commit 473b93287.

Andrew Gierth, with kibitzing by me and others

Discussion: <87mvl5on7n.fsf@news-spur.riddles.org.uk>
This commit is contained in:
Tom Lane
2016-08-13 18:31:14 -04:00
parent 4997878193
commit ed0097e4f9
28 changed files with 1146 additions and 18 deletions
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27
src/backend/access/index/amapi.c
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@@ -47,9 +47,12 @@ GetIndexAmRoutine(Oid amhandler)
/*
* GetIndexAmRoutineByAmId - look up the handler of the index access method
* with the given OID, and get its IndexAmRoutine struct.
*
* If the given OID isn't a valid index access method, returns NULL if
* noerror is true, else throws error.
*/
IndexAmRoutine *
GetIndexAmRoutineByAmId(Oid amoid)
GetIndexAmRoutineByAmId(Oid amoid, bool noerror)
{
HeapTuple tuple;
Form_pg_am amform;
@@ -58,25 +61,43 @@ GetIndexAmRoutineByAmId(Oid amoid)
/* Get handler function OID for the access method */
tuple = SearchSysCache1(AMOID, ObjectIdGetDatum(amoid));
if (!HeapTupleIsValid(tuple))
{
if (noerror)
return NULL;
elog(ERROR, "cache lookup failed for access method %u",
amoid);
}
amform = (Form_pg_am) GETSTRUCT(tuple);
/* Check if it's index access method */
/* Check if it's an index access method as opposed to some other AM */
if (amform->amtype != AMTYPE_INDEX)
{
if (noerror)
{
ReleaseSysCache(tuple);
return NULL;
}
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("access method \"%s\" is not of type %s",
NameStr(amform->amname), "INDEX")));
}
amhandler = amform->amhandler;
/* Complain if handler OID is invalid */
if (!RegProcedureIsValid(amhandler))
{
if (noerror)
{
ReleaseSysCache(tuple);
return NULL;
}
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("index access method \"%s\" does not have a handler",
NameStr(amform->amname))));
}
ReleaseSysCache(tuple);
@@ -107,7 +128,7 @@ amvalidate(PG_FUNCTION_ARGS)
ReleaseSysCache(classtup);
amroutine = GetIndexAmRoutineByAmId(amoid);
amroutine = GetIndexAmRoutineByAmId(amoid, false);
if (amroutine->amvalidate == NULL)
elog(ERROR, "function amvalidate is not defined for index access method %u",