pg_publication.c

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/*-------------------------------------------------------------------------
 *
 * pg_publication.c
 *      publication C API manipulation
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *      pg_publication.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/tableam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/objectaccess.h"
#include "catalog/objectaddress.h"
#include "catalog/pg_publication.h"
#include "catalog/pg_publication_rel.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"

/*
 * Check if relation can be in given publication and throws appropriate
 * error if not.
 */
static void
check_publication_add_relation(Relation targetrel)
{
    /* Give more specific error for partitioned tables */
    if (RelationGetForm(targetrel)->relkind == RELKIND_PARTITIONED_TABLE)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("\"%s\" is a partitioned table",
                        RelationGetRelationName(targetrel)),
                 errdetail("Adding partitioned tables to publications is not supported."),
                 errhint("You can add the table partitions individually.")));

    /* Must be table */
    if (RelationGetForm(targetrel)->relkind != RELKIND_RELATION)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("\"%s\" is not a table",
                        RelationGetRelationName(targetrel)),
                 errdetail("Only tables can be added to publications.")));

    /* Can't be system table */
    if (IsCatalogRelation(targetrel))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("\"%s\" is a system table",
                        RelationGetRelationName(targetrel)),
                 errdetail("System tables cannot be added to publications.")));

    /* UNLOGGED and TEMP relations cannot be part of publication. */
    if (!RelationNeedsWAL(targetrel))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("table \"%s\" cannot be replicated",
                        RelationGetRelationName(targetrel)),
                 errdetail("Temporary and unlogged relations cannot be replicated.")));
}

/*
 * Returns if relation represented by oid and Form_pg_class entry
 * is publishable.
 *
 * Does same checks as the above, but does not need relation to be opened
 * and also does not throw errors.
 *
 * XXX  This also excludes all tables with relid < FirstNormalObjectId,
 * ie all tables created during initdb.  This mainly affects the preinstalled
 * information_schema.  IsCatalogRelationOid() only excludes tables with
 * relid < FirstBootstrapObjectId, making that test rather redundant,
 * but really we should get rid of the FirstNormalObjectId test not
 * IsCatalogRelationOid.  We can't do so today because we don't want
 * information_schema tables to be considered publishable; but this test
 * is really inadequate for that, since the information_schema could be
 * dropped and reloaded and then it'll be considered publishable.  The best
 * long-term solution may be to add a "relispublishable" bool to pg_class,
 * and depend on that instead of OID checks.
 */
static bool
is_publishable_class(Oid relid, Form_pg_class reltuple)
{
    return reltuple->relkind == RELKIND_RELATION &&
        !IsCatalogRelationOid(relid) &&
        reltuple->relpersistence == RELPERSISTENCE_PERMANENT &&
        relid >= FirstNormalObjectId;
}

/*
 * Another variant of this, taking a Relation.
 */
bool
is_publishable_relation(Relation rel)
{
    return is_publishable_class(RelationGetRelid(rel), rel->rd_rel);
}


/*
 * SQL-callable variant of the above
 *
 * This returns null when the relation does not exist.  This is intended to be
 * used for example in psql to avoid gratuitous errors when there are
 * concurrent catalog changes.
 */
Datum
pg_relation_is_publishable(PG_FUNCTION_ARGS)
{
    Oid         relid = PG_GETARG_OID(0);
    HeapTuple   tuple;
    bool        result;

    tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    if (!HeapTupleIsValid(tuple))
        PG_RETURN_NULL();
    result = is_publishable_class(relid, (Form_pg_class) GETSTRUCT(tuple));
    ReleaseSysCache(tuple);
    PG_RETURN_BOOL(result);
}


/*
 * Insert new publication / relation mapping.
 */
ObjectAddress
publication_add_relation(Oid pubid, Relation targetrel,
                         bool if_not_exists)
{
    Relation    rel;
    HeapTuple   tup;
    Datum       values[Natts_pg_publication_rel];
    bool        nulls[Natts_pg_publication_rel];
    Oid         relid = RelationGetRelid(targetrel);
    Oid         prrelid;
    Publication *pub = GetPublication(pubid);
    ObjectAddress myself,
                referenced;

    rel = table_open(PublicationRelRelationId, RowExclusiveLock);

    /*
     * Check for duplicates. Note that this does not really prevent
     * duplicates, it's here just to provide nicer error message in common
     * case. The real protection is the unique key on the catalog.
     */
    if (SearchSysCacheExists2(PUBLICATIONRELMAP, ObjectIdGetDatum(relid),
                              ObjectIdGetDatum(pubid)))
    {
        table_close(rel, RowExclusiveLock);

        if (if_not_exists)
            return InvalidObjectAddress;

        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("relation \"%s\" is already member of publication \"%s\"",
                        RelationGetRelationName(targetrel), pub->name)));
    }

    check_publication_add_relation(targetrel);

    /* Form a tuple. */
    memset(values, 0, sizeof(values));
    memset(nulls, false, sizeof(nulls));

    prrelid = GetNewOidWithIndex(rel, PublicationRelObjectIndexId,
                                 Anum_pg_publication_rel_oid);
    values[Anum_pg_publication_rel_oid - 1] = ObjectIdGetDatum(prrelid);
    values[Anum_pg_publication_rel_prpubid - 1] =
        ObjectIdGetDatum(pubid);
    values[Anum_pg_publication_rel_prrelid - 1] =
        ObjectIdGetDatum(relid);

    tup = heap_form_tuple(RelationGetDescr(rel), values, nulls);

    /* Insert tuple into catalog. */
    CatalogTupleInsert(rel, tup);
    heap_freetuple(tup);

    ObjectAddressSet(myself, PublicationRelRelationId, prrelid);

    /* Add dependency on the publication */
    ObjectAddressSet(referenced, PublicationRelationId, pubid);
    recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);

    /* Add dependency on the relation */
    ObjectAddressSet(referenced, RelationRelationId, relid);
    recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);

    /* Close the table. */
    table_close(rel, RowExclusiveLock);

    /* Invalidate relcache so that publication info is rebuilt. */
    CacheInvalidateRelcache(targetrel);

    return myself;
}


/*
 * Gets list of publication oids for a relation oid.
 */
List *
GetRelationPublications(Oid relid)
{
    List       *result = NIL;
    CatCList   *pubrellist;
    int         i;

    /* Find all publications associated with the relation. */
    pubrellist = SearchSysCacheList1(PUBLICATIONRELMAP,
                                     ObjectIdGetDatum(relid));
    for (i = 0; i < pubrellist->n_members; i++)
    {
        HeapTuple   tup = &pubrellist->members[i]->tuple;
        Oid         pubid = ((Form_pg_publication_rel) GETSTRUCT(tup))->prpubid;

        result = lappend_oid(result, pubid);
    }

    ReleaseSysCacheList(pubrellist);

    return result;
}

/*
 * Gets list of relation oids for a publication.
 *
 * This should only be used for normal publications, the FOR ALL TABLES
 * should use GetAllTablesPublicationRelations().
 */
List *
GetPublicationRelations(Oid pubid)
{
    List       *result;
    Relation    pubrelsrel;
    ScanKeyData scankey;
    SysScanDesc scan;
    HeapTuple   tup;

    /* Find all publications associated with the relation. */
    pubrelsrel = table_open(PublicationRelRelationId, AccessShareLock);

    ScanKeyInit(&scankey,
                Anum_pg_publication_rel_prpubid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(pubid));

    scan = systable_beginscan(pubrelsrel, PublicationRelPrrelidPrpubidIndexId,
                              true, NULL, 1, &scankey);

    result = NIL;
    while (HeapTupleIsValid(tup = systable_getnext(scan)))
    {
        Form_pg_publication_rel pubrel;

        pubrel = (Form_pg_publication_rel) GETSTRUCT(tup);

        result = lappend_oid(result, pubrel->prrelid);
    }

    systable_endscan(scan);
    table_close(pubrelsrel, AccessShareLock);

    return result;
}

/*
 * Gets list of publication oids for publications marked as FOR ALL TABLES.
 */
List *
GetAllTablesPublications(void)
{
    List       *result;
    Relation    rel;
    ScanKeyData scankey;
    SysScanDesc scan;
    HeapTuple   tup;

    /* Find all publications that are marked as for all tables. */
    rel = table_open(PublicationRelationId, AccessShareLock);

    ScanKeyInit(&scankey,
                Anum_pg_publication_puballtables,
                BTEqualStrategyNumber, F_BOOLEQ,
                BoolGetDatum(true));

    scan = systable_beginscan(rel, InvalidOid, false,
                              NULL, 1, &scankey);

    result = NIL;
    while (HeapTupleIsValid(tup = systable_getnext(scan)))
    {
        Oid         oid = ((Form_pg_publication) GETSTRUCT(tup))->oid;

        result = lappend_oid(result, oid);
    }

    systable_endscan(scan);
    table_close(rel, AccessShareLock);

    return result;
}

/*
 * Gets list of all relation published by FOR ALL TABLES publication(s).
 */
List *
GetAllTablesPublicationRelations(void)
{
    Relation    classRel;
    ScanKeyData key[1];
    TableScanDesc scan;
    HeapTuple   tuple;
    List       *result = NIL;

    classRel = table_open(RelationRelationId, AccessShareLock);

    ScanKeyInit(&key[0],
                Anum_pg_class_relkind,
                BTEqualStrategyNumber, F_CHAREQ,
                CharGetDatum(RELKIND_RELATION));

    scan = table_beginscan_catalog(classRel, 1, key);

    while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
    {
        Form_pg_class relForm = (Form_pg_class) GETSTRUCT(tuple);
        Oid         relid = relForm->oid;

        if (is_publishable_class(relid, relForm))
            result = lappend_oid(result, relid);
    }

    table_endscan(scan);
    table_close(classRel, AccessShareLock);

    return result;
}

/*
 * Get publication using oid
 *
 * The Publication struct and its data are palloc'ed here.
 */
Publication *
GetPublication(Oid pubid)
{
    HeapTuple   tup;
    Publication *pub;
    Form_pg_publication pubform;

    tup = SearchSysCache1(PUBLICATIONOID, ObjectIdGetDatum(pubid));
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "cache lookup failed for publication %u", pubid);

    pubform = (Form_pg_publication) GETSTRUCT(tup);

    pub = (Publication *) palloc(sizeof(Publication));
    pub->oid = pubid;
    pub->name = pstrdup(NameStr(pubform->pubname));
    pub->alltables = pubform->puballtables;
    pub->pubactions.pubinsert = pubform->pubinsert;
    pub->pubactions.pubupdate = pubform->pubupdate;
    pub->pubactions.pubdelete = pubform->pubdelete;
    pub->pubactions.pubtruncate = pubform->pubtruncate;

    ReleaseSysCache(tup);

    return pub;
}


/*
 * Get Publication using name.
 */
Publication *
GetPublicationByName(const char *pubname, bool missing_ok)
{
    Oid         oid;

    oid = get_publication_oid(pubname, missing_ok);

    return OidIsValid(oid) ? GetPublication(oid) : NULL;
}

/*
 * get_publication_oid - given a publication name, look up the OID
 *
 * If missing_ok is false, throw an error if name not found.  If true, just
 * return InvalidOid.
 */
Oid
get_publication_oid(const char *pubname, bool missing_ok)
{
    Oid         oid;

    oid = GetSysCacheOid1(PUBLICATIONNAME, Anum_pg_publication_oid,
                          CStringGetDatum(pubname));
    if (!OidIsValid(oid) && !missing_ok)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("publication \"%s\" does not exist", pubname)));
    return oid;
}

/*
 * get_publication_name - given a publication Oid, look up the name
 *
 * If missing_ok is false, throw an error if name not found.  If true, just
 * return NULL.
 */
char *
get_publication_name(Oid pubid, bool missing_ok)
{
    HeapTuple   tup;
    char       *pubname;
    Form_pg_publication pubform;

    tup = SearchSysCache1(PUBLICATIONOID, ObjectIdGetDatum(pubid));

    if (!HeapTupleIsValid(tup))
    {
        if (!missing_ok)
            elog(ERROR, "cache lookup failed for publication %u", pubid);
        return NULL;
    }

    pubform = (Form_pg_publication) GETSTRUCT(tup);
    pubname = pstrdup(NameStr(pubform->pubname));

    ReleaseSysCache(tup);

    return pubname;
}

/*
 * Returns Oids of tables in a publication.
 */
Datum
pg_get_publication_tables(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    char       *pubname = text_to_cstring(PG_GETARG_TEXT_PP(0));
    Publication *publication;
    List       *tables;

    /* stuff done only on the first call of the function */
    if (SRF_IS_FIRSTCALL())
    {
        MemoryContext oldcontext;

        /* create a function context for cross-call persistence */
        funcctx = SRF_FIRSTCALL_INIT();

        /* switch to memory context appropriate for multiple function calls */
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        publication = GetPublicationByName(pubname, false);
        if (publication->alltables)
            tables = GetAllTablesPublicationRelations();
        else
            tables = GetPublicationRelations(publication->oid);
        funcctx->user_fctx = (void *) tables;

        MemoryContextSwitchTo(oldcontext);
    }

    /* stuff done on every call of the function */
    funcctx = SRF_PERCALL_SETUP();
    tables = (List *) funcctx->user_fctx;

    if (funcctx->call_cntr < list_length(tables))
    {
        Oid         relid = list_nth_oid(tables, funcctx->call_cntr);

        SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(relid));
    }

    SRF_RETURN_DONE(funcctx);
}