pg_collation.c

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/*-------------------------------------------------------------------------
 *
 * pg_collation.c
 *    routines to support manipulation of the pg_collation relation
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/catalog/pg_collation.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_collation_fn.h"
#include "catalog/pg_namespace.h"
#include "mb/pg_wchar.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/tqual.h"


/*
 * CollationCreate
 *
 * Add a new tuple to pg_collation.
 */
Oid
CollationCreate(const char *collname, Oid collnamespace,
                Oid collowner,
                int32 collencoding,
                const char *collcollate, const char *collctype)
{
    Relation    rel;
    TupleDesc   tupDesc;
    HeapTuple   tup;
    Datum       values[Natts_pg_collation];
    bool        nulls[Natts_pg_collation];
    NameData    name_name,
                name_collate,
                name_ctype;
    Oid         oid;
    ObjectAddress myself,
                referenced;

    AssertArg(collname);
    AssertArg(collnamespace);
    AssertArg(collowner);
    AssertArg(collcollate);
    AssertArg(collctype);

    /*
     * Make sure there is no existing collation of same name & encoding.
     *
     * This would be caught by the unique index anyway; we're just giving a
     * friendlier error message.  The unique index provides a backstop against
     * race conditions.
     */
    if (SearchSysCacheExists3(COLLNAMEENCNSP,
                              PointerGetDatum(collname),
                              Int32GetDatum(collencoding),
                              ObjectIdGetDatum(collnamespace)))
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("collation \"%s\" for encoding \"%s\" already exists",
                        collname, pg_encoding_to_char(collencoding))));

    /*
     * Also forbid matching an any-encoding entry.  This test of course is not
     * backed up by the unique index, but it's not a problem since we don't
     * support adding any-encoding entries after initdb.
     */
    if (SearchSysCacheExists3(COLLNAMEENCNSP,
                              PointerGetDatum(collname),
                              Int32GetDatum(-1),
                              ObjectIdGetDatum(collnamespace)))
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("collation \"%s\" already exists",
                        collname)));

    /* open pg_collation */
    rel = heap_open(CollationRelationId, RowExclusiveLock);
    tupDesc = RelationGetDescr(rel);

    /* form a tuple */
    memset(nulls, 0, sizeof(nulls));

    namestrcpy(&name_name, collname);
    values[Anum_pg_collation_collname - 1] = NameGetDatum(&name_name);
    values[Anum_pg_collation_collnamespace - 1] = ObjectIdGetDatum(collnamespace);
    values[Anum_pg_collation_collowner - 1] = ObjectIdGetDatum(collowner);
    values[Anum_pg_collation_collencoding - 1] = Int32GetDatum(collencoding);
    namestrcpy(&name_collate, collcollate);
    values[Anum_pg_collation_collcollate - 1] = NameGetDatum(&name_collate);
    namestrcpy(&name_ctype, collctype);
    values[Anum_pg_collation_collctype - 1] = NameGetDatum(&name_ctype);

    tup = heap_form_tuple(tupDesc, values, nulls);

    /* insert a new tuple */
    oid = simple_heap_insert(rel, tup);
    Assert(OidIsValid(oid));

    /* update the index if any */
    CatalogUpdateIndexes(rel, tup);

    /* set up dependencies for the new collation */
    myself.classId = CollationRelationId;
    myself.objectId = oid;
    myself.objectSubId = 0;

    /* create dependency on namespace */
    referenced.classId = NamespaceRelationId;
    referenced.objectId = collnamespace;
    referenced.objectSubId = 0;
    recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);

    /* create dependency on owner */
    recordDependencyOnOwner(CollationRelationId, HeapTupleGetOid(tup),
                            collowner);

    /* dependency on extension */
    recordDependencyOnCurrentExtension(&myself, false);

    /* Post creation hook for new collation */
    InvokeObjectPostCreateHook(CollationRelationId, oid, 0);

    heap_freetuple(tup);
    heap_close(rel, RowExclusiveLock);

    return oid;
}

/*
 * RemoveCollationById
 *
 * Remove a tuple from pg_collation by Oid. This function is solely
 * called inside catalog/dependency.c
 */
void
RemoveCollationById(Oid collationOid)
{
    Relation    rel;
    ScanKeyData scanKeyData;
    SysScanDesc scandesc;
    HeapTuple   tuple;

    rel = heap_open(CollationRelationId, RowExclusiveLock);

    ScanKeyInit(&scanKeyData,
                ObjectIdAttributeNumber,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(collationOid));

    scandesc = systable_beginscan(rel, CollationOidIndexId, true,
                                  SnapshotNow, 1, &scanKeyData);

    tuple = systable_getnext(scandesc);

    if (HeapTupleIsValid(tuple))
        simple_heap_delete(rel, &tuple->t_self);
    else
        elog(ERROR, "could not find tuple for collation %u", collationOid);

    systable_endscan(scandesc);

    heap_close(rel, RowExclusiveLock);
}