relation.c

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/*-------------------------------------------------------------------------
 * relation.c
 *     PostgreSQL logical replication relation mapping cache
 *
 * Copyright (c) 2016-2021, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/replication/logical/relation.c
 *
 * NOTES
 *    Routines in this file mainly have to do with mapping the properties
 *    of local replication target relations to the properties of their
 *    remote counterpart.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.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/inval.h"


static MemoryContext LogicalRepRelMapContext = NULL;

static HTAB *LogicalRepRelMap = NULL;

/*
 * Partition map (LogicalRepPartMap)
 *
 * When a partitioned table is used as replication target, replicated
 * operations are actually performed on its leaf partitions, which requires
 * the partitions to also be mapped to the remote relation.  Parent's entry
 * (LogicalRepRelMapEntry) cannot be used as-is for all partitions, because
 * individual partitions may have different attribute numbers, which means
 * attribute mappings to remote relation's attributes must be maintained
 * separately for each partition.
 */
static MemoryContext LogicalRepPartMapContext = NULL;
static HTAB *LogicalRepPartMap = NULL;
typedef struct LogicalRepPartMapEntry
{
    Oid         partoid;        /* LogicalRepPartMap's key */
    LogicalRepRelMapEntry relmapentry;
} LogicalRepPartMapEntry;

/*
 * 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->localrelvalid = false;
                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->localrelvalid = false;
    }
}

/*
 * 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. */
    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);

    /* 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;
}

/*
 * Report error with names of the missing local relation column(s), if any.
 */
static void
logicalrep_report_missing_attrs(LogicalRepRelation *remoterel,
                                Bitmapset *missingatts)
{
    if (!bms_is_empty(missingatts))
    {
        StringInfoData missingattsbuf;
        int         missingattcnt = 0;
        int         i;

        initStringInfo(&missingattsbuf);

        while ((i = bms_first_member(missingatts)) >= 0)
        {
            missingattcnt++;
            if (missingattcnt == 1)
                appendStringInfo(&missingattsbuf, _("\"%s\""),
                                 remoterel->attnames[i]);
            else
                appendStringInfo(&missingattsbuf, _(", \"%s\""),
                                 remoterel->attnames[i]);
        }

        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg_plural("logical replication target relation \"%s.%s\" is missing replicated column: %s",
                               "logical replication target relation \"%s.%s\" is missing replicated columns: %s",
                               missingattcnt,
                               remoterel->nspname,
                               remoterel->relname,
                               missingattsbuf.data)));
    }
}

/*
 * Open the local relation associated with the remote one.
 *
 * Rebuilds the Relcache mapping if it was invalidated by local DDL.
 */
LogicalRepRelMapEntry *
logicalrep_rel_open(LogicalRepRelId remoteid, LOCKMODE lockmode)
{
    LogicalRepRelMapEntry *entry;
    bool        found;
    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;

    /* Ensure we don't leak a relcache refcount. */
    if (entry->localrel)
        elog(ERROR, "remote relation ID %u is already open", remoteid);

    /*
     * When opening and locking a relation, pending invalidation messages are
     * processed which can invalidate the relation.  Hence, if the entry is
     * currently considered valid, try to open the local relation by OID and
     * see if invalidation ensues.
     */
    if (entry->localrelvalid)
    {
        entry->localrel = try_table_open(entry->localreloid, lockmode);
        if (!entry->localrel)
        {
            /* Table was renamed or dropped. */
            entry->localrelvalid = false;
        }
        else if (!entry->localrelvalid)
        {
            /* Note we release the no-longer-useful lock here. */
            table_close(entry->localrel, lockmode);
            entry->localrel = NULL;
        }
    }

    /*
     * If the entry has been marked invalid since we last had lock on it,
     * re-open the local relation by name and rebuild all derived data.
     */
    if (!entry->localrelvalid)
    {
        Oid         relid;
        Bitmapset  *idkey;
        TupleDesc   desc;
        MemoryContext oldctx;
        int         i;
        Bitmapset  *missingatts;

        /* 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);
        entry->localreloid = relid;

        /* 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);

        /* check and report missing attrs, if any */
        missingatts = bms_add_range(NULL, 0, remoterel->natts - 1);
        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)
                missingatts = bms_del_member(missingatts, attnum);
        }

        logicalrep_report_missing_attrs(remoterel, missingatts);

        /* be tidy */
        bms_free(missingatts);

        /*
         * 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->localrelvalid = true;
    }

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

    return entry;
}

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

/*
 * Partition cache: look up partition LogicalRepRelMapEntry's
 *
 * Unlike relation map cache, this is keyed by partition OID, not remote
 * relation OID, because we only have to use this cache in the case where
 * partitions are not directly mapped to any remote relation, such as when
 * replication is occurring with one of their ancestors as target.
 */

/*
 * Relcache invalidation callback
 */
static void
logicalrep_partmap_invalidate_cb(Datum arg, Oid reloid)
{
    LogicalRepRelMapEntry *entry;

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

    if (reloid != InvalidOid)
    {
        HASH_SEQ_STATUS status;

        hash_seq_init(&status, LogicalRepPartMap);

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

        hash_seq_init(&status, LogicalRepPartMap);

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

/*
 * Initialize the partition map cache.
 */
static void
logicalrep_partmap_init(void)
{
    HASHCTL     ctl;

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

    /* Initialize the relation hash table. */
    ctl.keysize = sizeof(Oid);  /* partition OID */
    ctl.entrysize = sizeof(LogicalRepPartMapEntry);
    ctl.hcxt = LogicalRepPartMapContext;

    LogicalRepPartMap = hash_create("logicalrep partition map cache", 64, &ctl,
                                    HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

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

/*
 * logicalrep_partition_open
 *
 * Returned entry reuses most of the values of the root table's entry, save
 * the attribute map, which can be different for the partition.  However,
 * we must physically copy all the data, in case the root table's entry
 * gets freed/rebuilt.
 *
 * Note there's no logicalrep_partition_close, because the caller closes the
 * component relation.
 */
LogicalRepRelMapEntry *
logicalrep_partition_open(LogicalRepRelMapEntry *root,
                          Relation partrel, AttrMap *map)
{
    LogicalRepRelMapEntry *entry;
    LogicalRepPartMapEntry *part_entry;
    LogicalRepRelation *remoterel = &root->remoterel;
    Oid         partOid = RelationGetRelid(partrel);
    AttrMap    *attrmap = root->attrmap;
    bool        found;
    int         i;
    MemoryContext oldctx;

    if (LogicalRepPartMap == NULL)
        logicalrep_partmap_init();

    /* Search for existing entry. */
    part_entry = (LogicalRepPartMapEntry *) hash_search(LogicalRepPartMap,
                                                        (void *) &partOid,
                                                        HASH_ENTER, &found);

    if (found)
        return &part_entry->relmapentry;

    memset(part_entry, 0, sizeof(LogicalRepPartMapEntry));

    /* Switch to longer-lived context. */
    oldctx = MemoryContextSwitchTo(LogicalRepPartMapContext);

    part_entry->partoid = partOid;

    /* Remote relation is copied as-is from the root entry. */
    entry = &part_entry->relmapentry;
    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);

    entry->localrel = partrel;
    entry->localreloid = partOid;

    /*
     * If the partition's attributes don't match the root relation's, we'll
     * need to make a new attrmap which maps partition attribute numbers to
     * remoterel's, instead of the original which maps root relation's
     * attribute numbers to remoterel's.
     *
     * Note that 'map' which comes from the tuple routing data structure
     * contains 1-based attribute numbers (of the parent relation).  However,
     * the map in 'entry', a logical replication data structure, contains
     * 0-based attribute numbers (of the remote relation).
     */
    if (map)
    {
        AttrNumber  attno;

        entry->attrmap = make_attrmap(map->maplen);
        for (attno = 0; attno < entry->attrmap->maplen; attno++)
        {
            AttrNumber  root_attno = map->attnums[attno];

            entry->attrmap->attnums[attno] = attrmap->attnums[root_attno - 1];
        }
    }
    else
    {
        /* Lacking copy_attmap, do this the hard way. */
        entry->attrmap = make_attrmap(attrmap->maplen);
        memcpy(entry->attrmap->attnums, attrmap->attnums,
               attrmap->maplen * sizeof(AttrNumber));
    }

    entry->updatable = root->updatable;

    entry->localrelvalid = true;

    /* state and statelsn are left set to 0. */
    MemoryContextSwitchTo(oldctx);

    return entry;
}