relation.c

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/*-------------------------------------------------------------------------
 * relation.c
 *     PostgreSQL logical replication
 *
 * Copyright (c) 2016-2020, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/replication/logical/relation.c
 *
 * NOTES
 *    This file contains helper functions for logical replication relation
 *    mapping cache.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/namespace.h"
#include "catalog/pg_subscription_rel.h"
#include "executor/executor.h"
#include "nodes/makefuncs.h"
#include "replication/logicalrelation.h"
#include "replication/worker_internal.h"
#include "utils/builtins.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/syscache.h"

static MemoryContext LogicalRepRelMapContext = NULL;

static HTAB *LogicalRepRelMap = NULL;
static HTAB *LogicalRepTypMap = NULL;


/*
 * Relcache invalidation callback for our relation map cache.
 */
static void
logicalrep_relmap_invalidate_cb(Datum arg, Oid reloid)
{
    LogicalRepRelMapEntry *entry;

    /* Just to be sure. */
    if (LogicalRepRelMap == NULL)
        return;

    if (reloid != InvalidOid)
    {
        HASH_SEQ_STATUS status;

        hash_seq_init(&status, LogicalRepRelMap);

        /* TODO, use inverse lookup hashtable? */
        while ((entry = (LogicalRepRelMapEntry *) hash_seq_search(&status)) != NULL)
        {
            if (entry->localreloid == reloid)
            {
                entry->localreloid = InvalidOid;
                hash_seq_term(&status);
                break;
            }
        }
    }
    else
    {
        /* invalidate all cache entries */
        HASH_SEQ_STATUS status;

        hash_seq_init(&status, LogicalRepRelMap);

        while ((entry = (LogicalRepRelMapEntry *) hash_seq_search(&status)) != NULL)
            entry->localreloid = InvalidOid;
    }
}

/*
 * Initialize the relation map cache.
 */
static void
logicalrep_relmap_init(void)
{
    HASHCTL     ctl;

    if (!LogicalRepRelMapContext)
        LogicalRepRelMapContext =
            AllocSetContextCreate(CacheMemoryContext,
                                  "LogicalRepRelMapContext",
                                  ALLOCSET_DEFAULT_SIZES);

    /* Initialize the relation hash table. */
    MemSet(&ctl, 0, sizeof(ctl));
    ctl.keysize = sizeof(LogicalRepRelId);
    ctl.entrysize = sizeof(LogicalRepRelMapEntry);
    ctl.hcxt = LogicalRepRelMapContext;

    LogicalRepRelMap = hash_create("logicalrep relation map cache", 128, &ctl,
                                   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

    /* Initialize the type hash table. */
    MemSet(&ctl, 0, sizeof(ctl));
    ctl.keysize = sizeof(Oid);
    ctl.entrysize = sizeof(LogicalRepTyp);
    ctl.hcxt = LogicalRepRelMapContext;

    /* This will usually be small. */
    LogicalRepTypMap = hash_create("logicalrep type map cache", 2, &ctl,
                                   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

    /* Watch for invalidation events. */
    CacheRegisterRelcacheCallback(logicalrep_relmap_invalidate_cb,
                                  (Datum) 0);
}

/*
 * Free the entry of a relation map cache.
 */
static void
logicalrep_relmap_free_entry(LogicalRepRelMapEntry *entry)
{
    LogicalRepRelation *remoterel;

    remoterel = &entry->remoterel;

    pfree(remoterel->nspname);
    pfree(remoterel->relname);

    if (remoterel->natts > 0)
    {
        int         i;

        for (i = 0; i < remoterel->natts; i++)
            pfree(remoterel->attnames[i]);

        pfree(remoterel->attnames);
        pfree(remoterel->atttyps);
    }
    bms_free(remoterel->attkeys);

    if (entry->attrmap)
        pfree(entry->attrmap);
}

/*
 * Add new entry or update existing entry in the relation map cache.
 *
 * Called when new relation mapping is sent by the publisher to update
 * our expected view of incoming data from said publisher.
 */
void
logicalrep_relmap_update(LogicalRepRelation *remoterel)
{
    MemoryContext oldctx;
    LogicalRepRelMapEntry *entry;
    bool        found;
    int         i;

    if (LogicalRepRelMap == NULL)
        logicalrep_relmap_init();

    /*
     * HASH_ENTER returns the existing entry if present or creates a new one.
     */
    entry = hash_search(LogicalRepRelMap, (void *) &remoterel->remoteid,
                        HASH_ENTER, &found);

    if (found)
        logicalrep_relmap_free_entry(entry);

    memset(entry, 0, sizeof(LogicalRepRelMapEntry));

    /* Make cached copy of the data */
    oldctx = MemoryContextSwitchTo(LogicalRepRelMapContext);
    entry->remoterel.remoteid = remoterel->remoteid;
    entry->remoterel.nspname = pstrdup(remoterel->nspname);
    entry->remoterel.relname = pstrdup(remoterel->relname);
    entry->remoterel.natts = remoterel->natts;
    entry->remoterel.attnames = palloc(remoterel->natts * sizeof(char *));
    entry->remoterel.atttyps = palloc(remoterel->natts * sizeof(Oid));
    for (i = 0; i < remoterel->natts; i++)
    {
        entry->remoterel.attnames[i] = pstrdup(remoterel->attnames[i]);
        entry->remoterel.atttyps[i] = remoterel->atttyps[i];
    }
    entry->remoterel.replident = remoterel->replident;
    entry->remoterel.attkeys = bms_copy(remoterel->attkeys);
    MemoryContextSwitchTo(oldctx);
}

/*
 * Find attribute index in TupleDesc struct by attribute name.
 *
 * Returns -1 if not found.
 */
static int
logicalrep_rel_att_by_name(LogicalRepRelation *remoterel, const char *attname)
{
    int         i;

    for (i = 0; i < remoterel->natts; i++)
    {
        if (strcmp(remoterel->attnames[i], attname) == 0)
            return i;
    }

    return -1;
}

/*
 * Open the local relation associated with the remote one.
 *
 * Optionally rebuilds the Relcache mapping if it was invalidated
 * by local DDL.
 */
LogicalRepRelMapEntry *
logicalrep_rel_open(LogicalRepRelId remoteid, LOCKMODE lockmode)
{
    LogicalRepRelMapEntry *entry;
    bool        found;
    Oid         relid = InvalidOid;
    LogicalRepRelation *remoterel;

    if (LogicalRepRelMap == NULL)
        logicalrep_relmap_init();

    /* Search for existing entry. */
    entry = hash_search(LogicalRepRelMap, (void *) &remoteid,
                        HASH_FIND, &found);

    if (!found)
        elog(ERROR, "no relation map entry for remote relation ID %u",
             remoteid);

    remoterel = &entry->remoterel;

    /*
     * When opening and locking a relation, pending invalidation messages are
     * processed which can invalidate the relation.  We need to update the
     * local cache both when we are first time accessing the relation and when
     * the relation is invalidated (aka entry->localreloid is set InvalidOid).
     */
    if (!OidIsValid(entry->localreloid))
    {
        /* Try to find and lock the relation by name. */
        relid = RangeVarGetRelid(makeRangeVar(remoterel->nspname,
                                              remoterel->relname, -1),
                                 lockmode, true);
        if (!OidIsValid(relid))
            ereport(ERROR,
                    (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                     errmsg("logical replication target relation \"%s.%s\" does not exist",
                            remoterel->nspname, remoterel->relname)));
        entry->localrel = table_open(relid, NoLock);

    }
    else
    {
        relid = entry->localreloid;
        entry->localrel = table_open(entry->localreloid, lockmode);
    }

    if (!OidIsValid(entry->localreloid))
    {
        int         found;
        Bitmapset  *idkey;
        TupleDesc   desc;
        MemoryContext oldctx;
        int         i;

        /* Check for supported relkind. */
        CheckSubscriptionRelkind(entry->localrel->rd_rel->relkind,
                                 remoterel->nspname, remoterel->relname);

        /*
         * Build the mapping of local attribute numbers to remote attribute
         * numbers and validate that we don't miss any replicated columns as
         * that would result in potentially unwanted data loss.
         */
        desc = RelationGetDescr(entry->localrel);
        oldctx = MemoryContextSwitchTo(LogicalRepRelMapContext);
        entry->attrmap = make_attrmap(desc->natts);
        MemoryContextSwitchTo(oldctx);

        found = 0;
        for (i = 0; i < desc->natts; i++)
        {
            int         attnum;
            Form_pg_attribute attr = TupleDescAttr(desc, i);

            if (attr->attisdropped || attr->attgenerated)
            {
                entry->attrmap->attnums[i] = -1;
                continue;
            }

            attnum = logicalrep_rel_att_by_name(remoterel,
                                                NameStr(attr->attname));

            entry->attrmap->attnums[i] = attnum;
            if (attnum >= 0)
                found++;
        }

        /* TODO, detail message with names of missing columns */
        if (found < remoterel->natts)
            ereport(ERROR,
                    (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                     errmsg("logical replication target relation \"%s.%s\" is missing "
                            "some replicated columns",
                            remoterel->nspname, remoterel->relname)));

        /*
         * Check that replica identity matches. We allow for stricter replica
         * identity (fewer columns) on subscriber as that will not stop us
         * from finding unique tuple. IE, if publisher has identity
         * (id,timestamp) and subscriber just (id) this will not be a problem,
         * but in the opposite scenario it will.
         *
         * Don't throw any error here just mark the relation entry as not
         * updatable, as replica identity is only for updates and deletes but
         * inserts can be replicated even without it.
         */
        entry->updatable = true;
        idkey = RelationGetIndexAttrBitmap(entry->localrel,
                                           INDEX_ATTR_BITMAP_IDENTITY_KEY);
        /* fallback to PK if no replica identity */
        if (idkey == NULL)
        {
            idkey = RelationGetIndexAttrBitmap(entry->localrel,
                                               INDEX_ATTR_BITMAP_PRIMARY_KEY);

            /*
             * If no replica identity index and no PK, the published table
             * must have replica identity FULL.
             */
            if (idkey == NULL && remoterel->replident != REPLICA_IDENTITY_FULL)
                entry->updatable = false;
        }

        i = -1;
        while ((i = bms_next_member(idkey, i)) >= 0)
        {
            int         attnum = i + FirstLowInvalidHeapAttributeNumber;

            if (!AttrNumberIsForUserDefinedAttr(attnum))
                ereport(ERROR,
                        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                         errmsg("logical replication target relation \"%s.%s\" uses "
                                "system columns in REPLICA IDENTITY index",
                                remoterel->nspname, remoterel->relname)));

            attnum = AttrNumberGetAttrOffset(attnum);

            if (entry->attrmap->attnums[attnum] < 0 ||
                !bms_is_member(entry->attrmap->attnums[attnum], remoterel->attkeys))
            {
                entry->updatable = false;
                break;
            }
        }

        entry->localreloid = relid;
    }

    if (entry->state != SUBREL_STATE_READY)
        entry->state = GetSubscriptionRelState(MySubscription->oid,
                                               entry->localreloid,
                                               &entry->statelsn,
                                               true);

    return entry;
}

/*
 * Close the previously opened logical relation.
 */
void
logicalrep_rel_close(LogicalRepRelMapEntry *rel, LOCKMODE lockmode)
{
    table_close(rel->localrel, lockmode);
    rel->localrel = NULL;
}

/*
 * Free the type map cache entry data.
 */
static void
logicalrep_typmap_free_entry(LogicalRepTyp *entry)
{
    pfree(entry->nspname);
    pfree(entry->typname);
}

/*
 * Add new entry or update existing entry in the type map cache.
 */
void
logicalrep_typmap_update(LogicalRepTyp *remotetyp)
{
    MemoryContext oldctx;
    LogicalRepTyp *entry;
    bool        found;

    if (LogicalRepTypMap == NULL)
        logicalrep_relmap_init();

    /*
     * HASH_ENTER returns the existing entry if present or creates a new one.
     */
    entry = hash_search(LogicalRepTypMap, (void *) &remotetyp->remoteid,
                        HASH_ENTER, &found);

    if (found)
        logicalrep_typmap_free_entry(entry);

    /* Make cached copy of the data */
    entry->remoteid = remotetyp->remoteid;
    oldctx = MemoryContextSwitchTo(LogicalRepRelMapContext);
    entry->nspname = pstrdup(remotetyp->nspname);
    entry->typname = pstrdup(remotetyp->typname);
    MemoryContextSwitchTo(oldctx);
}

/*
 * Fetch type name from the cache by remote type OID.
 *
 * Return a substitute value if we cannot find the data type; no message is
 * sent to the log in that case, because this is used by error callback
 * already.
 */
char *
logicalrep_typmap_gettypname(Oid remoteid)
{
    LogicalRepTyp *entry;
    bool        found;

    /* Internal types are mapped directly. */
    if (remoteid < FirstGenbkiObjectId)
    {
        if (!get_typisdefined(remoteid))
        {
            /*
             * This can be caused by having a publisher with a higher
             * PostgreSQL major version than the subscriber.
             */
            return psprintf("unrecognized %u", remoteid);
        }

        return format_type_be(remoteid);
    }

    if (LogicalRepTypMap == NULL)
    {
        /*
         * If the typemap is not initialized yet, we cannot possibly attempt
         * to search the hash table; but there's no way we know the type
         * locally yet, since we haven't received a message about this type,
         * so this is the best we can do.
         */
        return psprintf("unrecognized %u", remoteid);
    }

    /* search the mapping */
    entry = hash_search(LogicalRepTypMap, (void *) &remoteid,
                        HASH_FIND, &found);
    if (!found)
        return psprintf("unrecognized %u", remoteid);

    Assert(OidIsValid(entry->remoteid));
    return psprintf("%s.%s", entry->nspname, entry->typname);
}