relfilenumbermap.h File Reference

#include "common/relpath.h"

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Functions
Oid	RelidByRelfilenumber (Oid reltablespace, RelFileNumber relfilenumber)

Function Documentation

RelidByRelfilenumber()

Oid RelidByRelfilenumber	(	Oid	reltablespace,
		RelFileNumber	relfilenumber
	)

Definition at line 138 of file relfilenumbermap.c.

{
    RelfilenumberMapKey key;
    RelfilenumberMapEntry *entry;
    bool        found;
    SysScanDesc scandesc;
    Relation    relation;
    HeapTuple   ntp;
    ScanKeyData skey[2];
    Oid         relid;
 
    if (RelfilenumberMapHash == NULL)
        InitializeRelfilenumberMap();
 
    /* 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.relfilenumber = relfilenumber;
 
    /*
     * 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(RelfilenumberMapHash, &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 = RelationMapFilenumberToOid(relfilenumber, 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, relfilenumber_skey, sizeof(skey));
 
        /* set scan arguments */
        skey[0].sk_argument = ObjectIdGetDatum(reltablespace);
        skey[1].sk_argument = ObjectIdGetDatum(relfilenumber);
 
        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, relfilenumber %u",
                     reltablespace, relfilenumber);
            found = true;
 
            Assert(classform->reltablespace == reltablespace);
            Assert(classform->relfilenode == relfilenumber);
            relid = classform->oid;
        }
 
        systable_endscan(scandesc);
        table_close(relation, AccessShareLock);
 
        /* check for tables that are mapped but not shared */
        if (!found)
            relid = RelationMapFilenumberToOid(relfilenumber, 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(RelfilenumberMapHash, &key, HASH_ENTER, &found);
    if (found)
        elog(ERROR, "corrupted hashtable");
    entry->relid = relid;
 
    return relid;
}

References AccessShareLock, Assert(), elog(), ERROR, GETSTRUCT, HASH_ENTER, HASH_FIND, hash_search(), HeapTupleIsValid, InitializeRelfilenumberMap(), InvalidOid, sort-test::key, MemSet, MyDatabaseTableSpace, ObjectIdGetDatum(), RelationMapFilenumberToOid(), relfilenumber_skey, RelfilenumberMapHash, RelfilenumberMapEntry::relid, ScanKeyData::sk_argument, systable_beginscan(), systable_endscan(), systable_getnext(), table_close(), and table_open().

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