relfilenodemap.h File Reference

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Functions
Oid	RelidByRelfilenode (Oid reltablespace, Oid relfilenode)

Function Documentation

RelidByRelfilenode()

Oid RelidByRelfilenode	(	Oid	reltablespace,
		Oid	relfilenode
	)

Definition at line 138 of file relfilenodemap.c.

References AccessShareLock, Assert, ClassTblspcRelfilenodeIndexId, elog, ERROR, GETSTRUCT, HASH_ENTER, HASH_FIND, hash_search(), HeapTupleIsValid, InitializeRelfilenodeMap(), InvalidOid, sort-test::key, MemSet, MyDatabaseTableSpace, ObjectIdGetDatum, RelationMapFilenodeToOid(), RelfilenodeMapKey::relfilenode, RelfilenodeMapEntry::relid, RelfilenodeMapKey::reltablespace, ScanKeyData::sk_argument, systable_beginscan(), systable_endscan(), systable_getnext(), table_close(), and table_open().

Referenced by autoprewarm_database_main(), pg_filenode_relation(), and ReorderBufferProcessTXN().

{
    RelfilenodeMapKey key;
    RelfilenodeMapEntry *entry;
    bool        found;
    SysScanDesc scandesc;
    Relation    relation;
    HeapTuple   ntp;
    ScanKeyData skey[2];
    Oid         relid;

    if (RelfilenodeMapHash == NULL)
        InitializeRelfilenodeMap();

    /* pg_class will show 0 when the value is actually MyDatabaseTableSpace */
    if (reltablespace == MyDatabaseTableSpace)
        reltablespace = 0;

    MemSet(&key, 0, sizeof(key));
    key.reltablespace = reltablespace;
    key.relfilenode = relfilenode;

    /*
     * Check cache and return entry if one is found. Even if no target
     * relation can be found later on we store the negative match and return a
     * InvalidOid from cache. That's not really necessary for performance
     * since querying invalid values isn't supposed to be a frequent thing,
     * but it's basically free.
     */
    entry = hash_search(RelfilenodeMapHash, (void *) &key, HASH_FIND, &found);

    if (found)
        return entry->relid;

    /* ok, no previous cache entry, do it the hard way */

    /* initialize empty/negative cache entry before doing the actual lookups */
    relid = InvalidOid;

    if (reltablespace == GLOBALTABLESPACE_OID)
    {
        /*
         * Ok, shared table, check relmapper.
         */
        relid = RelationMapFilenodeToOid(relfilenode, true);
    }
    else
    {
        /*
         * Not a shared table, could either be a plain relation or a
         * non-shared, nailed one, like e.g. pg_class.
         */

        /* check for plain relations by looking in pg_class */
        relation = table_open(RelationRelationId, AccessShareLock);

        /* copy scankey to local copy, it will be modified during the scan */
        memcpy(skey, relfilenode_skey, sizeof(skey));

        /* set scan arguments */
        skey[0].sk_argument = ObjectIdGetDatum(reltablespace);
        skey[1].sk_argument = ObjectIdGetDatum(relfilenode);

        scandesc = systable_beginscan(relation,
                                      ClassTblspcRelfilenodeIndexId,
                                      true,
                                      NULL,
                                      2,
                                      skey);

        found = false;

        while (HeapTupleIsValid(ntp = systable_getnext(scandesc)))
        {
            Form_pg_class classform = (Form_pg_class) GETSTRUCT(ntp);

            if (found)
                elog(ERROR,
                     "unexpected duplicate for tablespace %u, relfilenode %u",
                     reltablespace, relfilenode);
            found = true;

            Assert(classform->reltablespace == reltablespace);
            Assert(classform->relfilenode == relfilenode);
            relid = classform->oid;
        }

        systable_endscan(scandesc);
        table_close(relation, AccessShareLock);

        /* check for tables that are mapped but not shared */
        if (!found)
            relid = RelationMapFilenodeToOid(relfilenode, false);
    }

    /*
     * Only enter entry into cache now, our opening of pg_class could have
     * caused cache invalidations to be executed which would have deleted a
     * new entry if we had entered it above.
     */
    entry = hash_search(RelfilenodeMapHash, (void *) &key, HASH_ENTER, &found);
    if (found)
        elog(ERROR, "corrupted hashtable");
    entry->relid = relid;

    return relid;
}