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913 lines
27 KiB
C
913 lines
27 KiB
C
/*-------------------------------------------------------------------------
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*
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* relmapper.c
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* Catalog-to-filenode mapping
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*
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* For most tables, the physical file underlying the table is specified by
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* pg_class.relfilenode. However, that obviously won't work for pg_class
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* itself, nor for the other "nailed" catalogs for which we have to be able
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* to set up working Relation entries without access to pg_class. It also
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* does not work for shared catalogs, since there is no practical way to
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* update other databases' pg_class entries when relocating a shared catalog.
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* Therefore, for these special catalogs (henceforth referred to as "mapped
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* catalogs") we rely on a separately maintained file that shows the mapping
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* from catalog OIDs to filenode numbers. Each database has a map file for
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* its local mapped catalogs, and there is a separate map file for shared
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* catalogs. Mapped catalogs have zero in their pg_class.relfilenode entries.
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*
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* Relocation of a normal table is committed (ie, the new physical file becomes
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* authoritative) when the pg_class row update commits. For mapped catalogs,
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* the act of updating the map file is effectively commit of the relocation.
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* We postpone the file update till just before commit of the transaction
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* doing the rewrite, but there is necessarily a window between. Therefore
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* mapped catalogs can only be relocated by operations such as VACUUM FULL
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* and CLUSTER, which make no transactionally-significant changes: it must be
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* safe for the new file to replace the old, even if the transaction itself
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* aborts. An important factor here is that the indexes and toast table of
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* a mapped catalog must also be mapped, so that the rewrites/relocations of
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* all these files commit in a single map file update rather than being tied
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* to transaction commit.
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*
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* Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/utils/cache/relmapper.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "access/xact.h"
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#include "catalog/catalog.h"
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#include "catalog/pg_tablespace.h"
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#include "catalog/storage.h"
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#include "miscadmin.h"
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#include "storage/fd.h"
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#include "storage/lwlock.h"
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#include "utils/inval.h"
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#include "utils/pg_crc.h"
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#include "utils/relmapper.h"
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/*
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* The map file is critical data: we have no automatic method for recovering
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* from loss or corruption of it. We use a CRC so that we can detect
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* corruption. To minimize the risk of failed updates, the map file should
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* be kept to no more than one standard-size disk sector (ie 512 bytes),
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* and we use overwrite-in-place rather than playing renaming games.
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* The struct layout below is designed to occupy exactly 512 bytes, which
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* might make filesystem updates a bit more efficient.
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*
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* Entries in the mappings[] array are in no particular order. We could
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* speed searching by insisting on OID order, but it really shouldn't be
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* worth the trouble given the intended size of the mapping sets.
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*/
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#define RELMAPPER_FILENAME "pg_filenode.map"
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#define RELMAPPER_FILEMAGIC 0x592717 /* version ID value */
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#define MAX_MAPPINGS 62 /* 62 * 8 + 16 = 512 */
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typedef struct RelMapping
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{
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Oid mapoid; /* OID of a catalog */
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Oid mapfilenode; /* its filenode number */
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} RelMapping;
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typedef struct RelMapFile
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{
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int32 magic; /* always RELMAPPER_FILEMAGIC */
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int32 num_mappings; /* number of valid RelMapping entries */
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RelMapping mappings[MAX_MAPPINGS];
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int32 crc; /* CRC of all above */
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int32 pad; /* to make the struct size be 512 exactly */
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} RelMapFile;
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/*
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* The currently known contents of the shared map file and our database's
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* local map file are stored here. These can be reloaded from disk
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* immediately whenever we receive an update sinval message.
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*/
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static RelMapFile shared_map;
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static RelMapFile local_map;
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/*
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* We use the same RelMapFile data structure to track uncommitted local
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* changes in the mappings (but note the magic and crc fields are not made
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* valid in these variables). Currently, map updates are not allowed within
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* subtransactions, so one set of transaction-level changes is sufficient.
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*
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* The active_xxx variables contain updates that are valid in our transaction
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* and should be honored by RelationMapOidToFilenode. The pending_xxx
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* variables contain updates we have been told about that aren't active yet;
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* they will become active at the next CommandCounterIncrement. This setup
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* lets map updates act similarly to updates of pg_class rows, ie, they
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* become visible only at the next CommandCounterIncrement boundary.
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*/
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static RelMapFile active_shared_updates;
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static RelMapFile active_local_updates;
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static RelMapFile pending_shared_updates;
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static RelMapFile pending_local_updates;
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/* non-export function prototypes */
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static void apply_map_update(RelMapFile *map, Oid relationId, Oid fileNode,
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bool add_okay);
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static void merge_map_updates(RelMapFile *map, const RelMapFile *updates,
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bool add_okay);
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static void load_relmap_file(bool shared);
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static void write_relmap_file(bool shared, RelMapFile *newmap,
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bool write_wal, bool send_sinval, bool preserve_files,
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Oid dbid, Oid tsid, const char *dbpath);
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static void perform_relmap_update(bool shared, const RelMapFile *updates);
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/*
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* RelationMapOidToFilenode
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*
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* The raison d' etre ... given a relation OID, look up its filenode.
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*
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* Although shared and local relation OIDs should never overlap, the caller
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* always knows which we need --- so pass that information to avoid useless
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* searching.
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*
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* Returns InvalidOid if the OID is not known (which should never happen,
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* but the caller is in a better position to report a meaningful error).
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*/
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Oid
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RelationMapOidToFilenode(Oid relationId, bool shared)
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{
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const RelMapFile *map;
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int32 i;
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/* If there are active updates, believe those over the main maps */
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if (shared)
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{
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map = &active_shared_updates;
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for (i = 0; i < map->num_mappings; i++)
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{
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if (relationId == map->mappings[i].mapoid)
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return map->mappings[i].mapfilenode;
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}
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map = &shared_map;
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for (i = 0; i < map->num_mappings; i++)
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{
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if (relationId == map->mappings[i].mapoid)
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return map->mappings[i].mapfilenode;
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}
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}
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else
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{
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map = &active_local_updates;
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for (i = 0; i < map->num_mappings; i++)
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{
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if (relationId == map->mappings[i].mapoid)
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return map->mappings[i].mapfilenode;
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}
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map = &local_map;
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for (i = 0; i < map->num_mappings; i++)
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{
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if (relationId == map->mappings[i].mapoid)
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return map->mappings[i].mapfilenode;
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}
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}
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return InvalidOid;
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}
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/*
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* RelationMapUpdateMap
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*
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* Install a new relfilenode mapping for the specified relation.
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*
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* If immediate is true (or we're bootstrapping), the mapping is activated
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* immediately. Otherwise it is made pending until CommandCounterIncrement.
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*/
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void
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RelationMapUpdateMap(Oid relationId, Oid fileNode, bool shared,
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bool immediate)
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{
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RelMapFile *map;
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if (IsBootstrapProcessingMode())
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{
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/*
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* In bootstrap mode, the mapping gets installed in permanent map.
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*/
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if (shared)
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map = &shared_map;
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else
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map = &local_map;
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}
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else
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{
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/*
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* We don't currently support map changes within subtransactions. This
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* could be done with more bookkeeping infrastructure, but it doesn't
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* presently seem worth it.
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*/
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if (GetCurrentTransactionNestLevel() > 1)
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elog(ERROR, "cannot change relation mapping within subtransaction");
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if (immediate)
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{
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/* Make it active, but only locally */
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if (shared)
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map = &active_shared_updates;
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else
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map = &active_local_updates;
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}
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else
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{
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/* Make it pending */
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if (shared)
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map = &pending_shared_updates;
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else
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map = &pending_local_updates;
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}
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}
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apply_map_update(map, relationId, fileNode, true);
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}
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/*
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* apply_map_update
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*
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* Insert a new mapping into the given map variable, replacing any existing
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* mapping for the same relation.
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*
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* In some cases the caller knows there must be an existing mapping; pass
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* add_okay = false to draw an error if not.
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*/
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static void
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apply_map_update(RelMapFile *map, Oid relationId, Oid fileNode, bool add_okay)
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{
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int32 i;
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/* Replace any existing mapping */
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for (i = 0; i < map->num_mappings; i++)
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{
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if (relationId == map->mappings[i].mapoid)
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{
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map->mappings[i].mapfilenode = fileNode;
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return;
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}
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}
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/* Nope, need to add a new mapping */
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if (!add_okay)
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elog(ERROR, "attempt to apply a mapping to unmapped relation %u",
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relationId);
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if (map->num_mappings >= MAX_MAPPINGS)
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elog(ERROR, "ran out of space in relation map");
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map->mappings[map->num_mappings].mapoid = relationId;
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map->mappings[map->num_mappings].mapfilenode = fileNode;
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map->num_mappings++;
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}
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/*
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* merge_map_updates
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*
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* Merge all the updates in the given pending-update map into the target map.
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* This is just a bulk form of apply_map_update.
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*/
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static void
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merge_map_updates(RelMapFile *map, const RelMapFile *updates, bool add_okay)
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{
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int32 i;
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for (i = 0; i < updates->num_mappings; i++)
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{
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apply_map_update(map,
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updates->mappings[i].mapoid,
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updates->mappings[i].mapfilenode,
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add_okay);
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}
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}
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/*
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* RelationMapRemoveMapping
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*
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* Remove a relation's entry in the map. This is only allowed for "active"
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* (but not committed) local mappings. We need it so we can back out the
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* entry for the transient target file when doing VACUUM FULL/CLUSTER on
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* a mapped relation.
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*/
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void
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RelationMapRemoveMapping(Oid relationId)
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{
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RelMapFile *map = &active_local_updates;
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int32 i;
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for (i = 0; i < map->num_mappings; i++)
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{
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if (relationId == map->mappings[i].mapoid)
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{
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/* Found it, collapse it out */
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map->mappings[i] = map->mappings[map->num_mappings - 1];
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map->num_mappings--;
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return;
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}
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}
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elog(ERROR, "could not find temporary mapping for relation %u",
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relationId);
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}
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/*
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* RelationMapInvalidate
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*
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* This routine is invoked for SI cache flush messages. We must re-read
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* the indicated map file. However, we might receive a SI message in a
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* process that hasn't yet, and might never, load the mapping files;
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* for example the autovacuum launcher, which *must not* try to read
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* a local map since it is attached to no particular database.
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* So, re-read only if the map is valid now.
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*/
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void
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RelationMapInvalidate(bool shared)
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{
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if (shared)
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{
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if (shared_map.magic == RELMAPPER_FILEMAGIC)
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load_relmap_file(true);
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}
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else
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{
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if (local_map.magic == RELMAPPER_FILEMAGIC)
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load_relmap_file(false);
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}
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}
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/*
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* RelationMapInvalidateAll
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*
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* Reload all map files. This is used to recover from SI message buffer
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* overflow: we can't be sure if we missed an inval message.
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* Again, reload only currently-valid maps.
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*/
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void
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RelationMapInvalidateAll(void)
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{
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if (shared_map.magic == RELMAPPER_FILEMAGIC)
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load_relmap_file(true);
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if (local_map.magic == RELMAPPER_FILEMAGIC)
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load_relmap_file(false);
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}
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/*
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* AtCCI_RelationMap
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*
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* Activate any "pending" relation map updates at CommandCounterIncrement time.
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*/
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void
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AtCCI_RelationMap(void)
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{
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if (pending_shared_updates.num_mappings != 0)
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{
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merge_map_updates(&active_shared_updates,
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&pending_shared_updates,
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true);
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pending_shared_updates.num_mappings = 0;
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}
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if (pending_local_updates.num_mappings != 0)
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{
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merge_map_updates(&active_local_updates,
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&pending_local_updates,
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true);
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pending_local_updates.num_mappings = 0;
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}
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}
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/*
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* AtEOXact_RelationMap
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*
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* Handle relation mapping at main-transaction commit or abort.
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*
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* During commit, this must be called as late as possible before the actual
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* transaction commit, so as to minimize the window where the transaction
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* could still roll back after committing map changes. Although nothing
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* critically bad happens in such a case, we still would prefer that it
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* not happen, since we'd possibly be losing useful updates to the relations'
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* pg_class row(s).
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*
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* During abort, we just have to throw away any pending map changes.
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* Normal post-abort cleanup will take care of fixing relcache entries.
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*/
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void
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AtEOXact_RelationMap(bool isCommit)
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{
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if (isCommit)
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{
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/*
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* We should not get here with any "pending" updates. (We could
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* logically choose to treat such as committed, but in the current
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* code this should never happen.)
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*/
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Assert(pending_shared_updates.num_mappings == 0);
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Assert(pending_local_updates.num_mappings == 0);
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/*
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* Write any active updates to the actual map files, then reset them.
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*/
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if (active_shared_updates.num_mappings != 0)
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{
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perform_relmap_update(true, &active_shared_updates);
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active_shared_updates.num_mappings = 0;
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}
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if (active_local_updates.num_mappings != 0)
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{
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perform_relmap_update(false, &active_local_updates);
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active_local_updates.num_mappings = 0;
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}
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}
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else
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{
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/* Abort --- drop all local and pending updates */
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active_shared_updates.num_mappings = 0;
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active_local_updates.num_mappings = 0;
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pending_shared_updates.num_mappings = 0;
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pending_local_updates.num_mappings = 0;
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}
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}
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/*
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* AtPrepare_RelationMap
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*
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* Handle relation mapping at PREPARE.
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*
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* Currently, we don't support preparing any transaction that changes the map.
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*/
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void
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AtPrepare_RelationMap(void)
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{
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if (active_shared_updates.num_mappings != 0 ||
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active_local_updates.num_mappings != 0 ||
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pending_shared_updates.num_mappings != 0 ||
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pending_local_updates.num_mappings != 0)
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ereport(ERROR,
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("cannot PREPARE a transaction that modified relation mapping")));
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}
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|
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/*
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* CheckPointRelationMap
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*
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* This is called during a checkpoint. It must ensure that any relation map
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* updates that were WAL-logged before the start of the checkpoint are
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* securely flushed to disk and will not need to be replayed later. This
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* seems unlikely to be a performance-critical issue, so we use a simple
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* method: we just take and release the RelationMappingLock. This ensures
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* that any already-logged map update is complete, because write_relmap_file
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* will fsync the map file before the lock is released.
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*/
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void
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CheckPointRelationMap(void)
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{
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LWLockAcquire(RelationMappingLock, LW_SHARED);
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LWLockRelease(RelationMappingLock);
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}
|
|
|
|
/*
|
|
* RelationMapFinishBootstrap
|
|
*
|
|
* Write out the initial relation mapping files at the completion of
|
|
* bootstrap. All the mapped files should have been made known to us
|
|
* via RelationMapUpdateMap calls.
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|
*/
|
|
void
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RelationMapFinishBootstrap(void)
|
|
{
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Assert(IsBootstrapProcessingMode());
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|
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/* Shouldn't be anything "pending" ... */
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Assert(active_shared_updates.num_mappings == 0);
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Assert(active_local_updates.num_mappings == 0);
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Assert(pending_shared_updates.num_mappings == 0);
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Assert(pending_local_updates.num_mappings == 0);
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|
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/* Write the files; no WAL or sinval needed */
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write_relmap_file(true, &shared_map, false, false, false,
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InvalidOid, GLOBALTABLESPACE_OID, NULL);
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write_relmap_file(false, &local_map, false, false, false,
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MyDatabaseId, MyDatabaseTableSpace, DatabasePath);
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}
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|
|
/*
|
|
* RelationMapInitialize
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*
|
|
* This initializes the mapper module at process startup. We can't access the
|
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* database yet, so just make sure the maps are empty.
|
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*/
|
|
void
|
|
RelationMapInitialize(void)
|
|
{
|
|
/* The static variables should initialize to zeroes, but let's be sure */
|
|
shared_map.magic = 0; /* mark it not loaded */
|
|
local_map.magic = 0;
|
|
shared_map.num_mappings = 0;
|
|
local_map.num_mappings = 0;
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|
active_shared_updates.num_mappings = 0;
|
|
active_local_updates.num_mappings = 0;
|
|
pending_shared_updates.num_mappings = 0;
|
|
pending_local_updates.num_mappings = 0;
|
|
}
|
|
|
|
/*
|
|
* RelationMapInitializePhase2
|
|
*
|
|
* This is called to prepare for access to pg_database during startup.
|
|
* We should be able to read the shared map file now.
|
|
*/
|
|
void
|
|
RelationMapInitializePhase2(void)
|
|
{
|
|
/*
|
|
* In bootstrap mode, the map file isn't there yet, so do nothing.
|
|
*/
|
|
if (IsBootstrapProcessingMode())
|
|
return;
|
|
|
|
/*
|
|
* Load the shared map file, die on error.
|
|
*/
|
|
load_relmap_file(true);
|
|
}
|
|
|
|
/*
|
|
* RelationMapInitializePhase3
|
|
*
|
|
* This is called as soon as we have determined MyDatabaseId and set up
|
|
* DatabasePath. At this point we should be able to read the local map file.
|
|
*/
|
|
void
|
|
RelationMapInitializePhase3(void)
|
|
{
|
|
/*
|
|
* In bootstrap mode, the map file isn't there yet, so do nothing.
|
|
*/
|
|
if (IsBootstrapProcessingMode())
|
|
return;
|
|
|
|
/*
|
|
* Load the local map file, die on error.
|
|
*/
|
|
load_relmap_file(false);
|
|
}
|
|
|
|
/*
|
|
* load_relmap_file -- load data from the shared or local map file
|
|
*
|
|
* Because the map file is essential for access to core system catalogs,
|
|
* failure to read it is a fatal error.
|
|
*
|
|
* Note that the local case requires DatabasePath to be set up.
|
|
*/
|
|
static void
|
|
load_relmap_file(bool shared)
|
|
{
|
|
RelMapFile *map;
|
|
char mapfilename[MAXPGPATH];
|
|
pg_crc32 crc;
|
|
int fd;
|
|
|
|
if (shared)
|
|
{
|
|
snprintf(mapfilename, sizeof(mapfilename), "global/%s",
|
|
RELMAPPER_FILENAME);
|
|
map = &shared_map;
|
|
}
|
|
else
|
|
{
|
|
snprintf(mapfilename, sizeof(mapfilename), "%s/%s",
|
|
DatabasePath, RELMAPPER_FILENAME);
|
|
map = &local_map;
|
|
}
|
|
|
|
/* Read data ... */
|
|
fd = BasicOpenFile(mapfilename, O_RDONLY | PG_BINARY, S_IRUSR | S_IWUSR);
|
|
if (fd < 0)
|
|
ereport(FATAL,
|
|
(errcode_for_file_access(),
|
|
errmsg("could not open relation mapping file \"%s\": %m",
|
|
mapfilename)));
|
|
|
|
/*
|
|
* Note: we could take RelationMappingLock in shared mode here, but it
|
|
* seems unnecessary since our read() should be atomic against any
|
|
* concurrent updater's write(). If the file is updated shortly after we
|
|
* look, the sinval signaling mechanism will make us re-read it before we
|
|
* are able to access any relation that's affected by the change.
|
|
*/
|
|
if (read(fd, map, sizeof(RelMapFile)) != sizeof(RelMapFile))
|
|
ereport(FATAL,
|
|
(errcode_for_file_access(),
|
|
errmsg("could not read relation mapping file \"%s\": %m",
|
|
mapfilename)));
|
|
|
|
close(fd);
|
|
|
|
/* check for correct magic number, etc */
|
|
if (map->magic != RELMAPPER_FILEMAGIC ||
|
|
map->num_mappings < 0 ||
|
|
map->num_mappings > MAX_MAPPINGS)
|
|
ereport(FATAL,
|
|
(errmsg("relation mapping file \"%s\" contains invalid data",
|
|
mapfilename)));
|
|
|
|
/* verify the CRC */
|
|
INIT_CRC32(crc);
|
|
COMP_CRC32(crc, (char *) map, offsetof(RelMapFile, crc));
|
|
FIN_CRC32(crc);
|
|
|
|
if (!EQ_CRC32(crc, map->crc))
|
|
ereport(FATAL,
|
|
(errmsg("relation mapping file \"%s\" contains incorrect checksum",
|
|
mapfilename)));
|
|
}
|
|
|
|
/*
|
|
* Write out a new shared or local map file with the given contents.
|
|
*
|
|
* The magic number and CRC are automatically updated in *newmap. On
|
|
* success, we copy the data to the appropriate permanent static variable.
|
|
*
|
|
* If write_wal is TRUE then an appropriate WAL message is emitted.
|
|
* (It will be false for bootstrap and WAL replay cases.)
|
|
*
|
|
* If send_sinval is TRUE then a SI invalidation message is sent.
|
|
* (This should be true except in bootstrap case.)
|
|
*
|
|
* If preserve_files is TRUE then the storage manager is warned not to
|
|
* delete the files listed in the map.
|
|
*
|
|
* Because this may be called during WAL replay when MyDatabaseId,
|
|
* DatabasePath, etc aren't valid, we require the caller to pass in suitable
|
|
* values. The caller is also responsible for being sure no concurrent
|
|
* map update could be happening.
|
|
*/
|
|
static void
|
|
write_relmap_file(bool shared, RelMapFile *newmap,
|
|
bool write_wal, bool send_sinval, bool preserve_files,
|
|
Oid dbid, Oid tsid, const char *dbpath)
|
|
{
|
|
int fd;
|
|
RelMapFile *realmap;
|
|
char mapfilename[MAXPGPATH];
|
|
|
|
/*
|
|
* Fill in the overhead fields and update CRC.
|
|
*/
|
|
newmap->magic = RELMAPPER_FILEMAGIC;
|
|
if (newmap->num_mappings < 0 || newmap->num_mappings > MAX_MAPPINGS)
|
|
elog(ERROR, "attempt to write bogus relation mapping");
|
|
|
|
INIT_CRC32(newmap->crc);
|
|
COMP_CRC32(newmap->crc, (char *) newmap, offsetof(RelMapFile, crc));
|
|
FIN_CRC32(newmap->crc);
|
|
|
|
/*
|
|
* Open the target file. We prefer to do this before entering the
|
|
* critical section, so that an open() failure need not force PANIC.
|
|
*
|
|
* Note: since we use BasicOpenFile, we are nominally responsible for
|
|
* ensuring the fd is closed on error. In practice, this isn't important
|
|
* because either an error happens inside the critical section, or we are
|
|
* in bootstrap or WAL replay; so an error past this point is always fatal
|
|
* anyway.
|
|
*/
|
|
if (shared)
|
|
{
|
|
snprintf(mapfilename, sizeof(mapfilename), "global/%s",
|
|
RELMAPPER_FILENAME);
|
|
realmap = &shared_map;
|
|
}
|
|
else
|
|
{
|
|
snprintf(mapfilename, sizeof(mapfilename), "%s/%s",
|
|
dbpath, RELMAPPER_FILENAME);
|
|
realmap = &local_map;
|
|
}
|
|
|
|
fd = BasicOpenFile(mapfilename,
|
|
O_WRONLY | O_CREAT | PG_BINARY,
|
|
S_IRUSR | S_IWUSR);
|
|
if (fd < 0)
|
|
ereport(ERROR,
|
|
(errcode_for_file_access(),
|
|
errmsg("could not open relation mapping file \"%s\": %m",
|
|
mapfilename)));
|
|
|
|
if (write_wal)
|
|
{
|
|
xl_relmap_update xlrec;
|
|
XLogRecData rdata[2];
|
|
XLogRecPtr lsn;
|
|
|
|
/* now errors are fatal ... */
|
|
START_CRIT_SECTION();
|
|
|
|
xlrec.dbid = dbid;
|
|
xlrec.tsid = tsid;
|
|
xlrec.nbytes = sizeof(RelMapFile);
|
|
|
|
rdata[0].data = (char *) (&xlrec);
|
|
rdata[0].len = MinSizeOfRelmapUpdate;
|
|
rdata[0].buffer = InvalidBuffer;
|
|
rdata[0].next = &(rdata[1]);
|
|
rdata[1].data = (char *) newmap;
|
|
rdata[1].len = sizeof(RelMapFile);
|
|
rdata[1].buffer = InvalidBuffer;
|
|
rdata[1].next = NULL;
|
|
|
|
lsn = XLogInsert(RM_RELMAP_ID, XLOG_RELMAP_UPDATE, rdata);
|
|
|
|
/* As always, WAL must hit the disk before the data update does */
|
|
XLogFlush(lsn);
|
|
}
|
|
|
|
errno = 0;
|
|
if (write(fd, newmap, sizeof(RelMapFile)) != sizeof(RelMapFile))
|
|
{
|
|
/* if write didn't set errno, assume problem is no disk space */
|
|
if (errno == 0)
|
|
errno = ENOSPC;
|
|
ereport(ERROR,
|
|
(errcode_for_file_access(),
|
|
errmsg("could not write to relation mapping file \"%s\": %m",
|
|
mapfilename)));
|
|
}
|
|
|
|
/*
|
|
* We choose to fsync the data to disk before considering the task done.
|
|
* It would be possible to relax this if it turns out to be a performance
|
|
* issue, but it would complicate checkpointing --- see notes for
|
|
* CheckPointRelationMap.
|
|
*/
|
|
if (pg_fsync(fd) != 0)
|
|
ereport(ERROR,
|
|
(errcode_for_file_access(),
|
|
errmsg("could not fsync relation mapping file \"%s\": %m",
|
|
mapfilename)));
|
|
|
|
if (close(fd))
|
|
ereport(ERROR,
|
|
(errcode_for_file_access(),
|
|
errmsg("could not close relation mapping file \"%s\": %m",
|
|
mapfilename)));
|
|
|
|
/*
|
|
* Now that the file is safely on disk, send sinval message to let other
|
|
* backends know to re-read it. We must do this inside the critical
|
|
* section: if for some reason we fail to send the message, we have to
|
|
* force a database-wide PANIC. Otherwise other backends might continue
|
|
* execution with stale mapping information, which would be catastrophic
|
|
* as soon as others began to use the now-committed data.
|
|
*/
|
|
if (send_sinval)
|
|
CacheInvalidateRelmap(dbid);
|
|
|
|
/*
|
|
* Make sure that the files listed in the map are not deleted if the outer
|
|
* transaction aborts. This had better be within the critical section
|
|
* too: it's not likely to fail, but if it did, we'd arrive at transaction
|
|
* abort with the files still vulnerable. PANICing will leave things in a
|
|
* good state on-disk.
|
|
*
|
|
* Note: we're cheating a little bit here by assuming that mapped files
|
|
* are either in pg_global or the database's default tablespace.
|
|
*/
|
|
if (preserve_files)
|
|
{
|
|
int32 i;
|
|
|
|
for (i = 0; i < newmap->num_mappings; i++)
|
|
{
|
|
RelFileNode rnode;
|
|
|
|
rnode.spcNode = tsid;
|
|
rnode.dbNode = dbid;
|
|
rnode.relNode = newmap->mappings[i].mapfilenode;
|
|
RelationPreserveStorage(rnode, false);
|
|
}
|
|
}
|
|
|
|
/* Success, update permanent copy */
|
|
memcpy(realmap, newmap, sizeof(RelMapFile));
|
|
|
|
/* Critical section done */
|
|
if (write_wal)
|
|
END_CRIT_SECTION();
|
|
}
|
|
|
|
/*
|
|
* Merge the specified updates into the appropriate "real" map,
|
|
* and write out the changes. This function must be used for committing
|
|
* updates during normal multiuser operation.
|
|
*/
|
|
static void
|
|
perform_relmap_update(bool shared, const RelMapFile *updates)
|
|
{
|
|
RelMapFile newmap;
|
|
|
|
/*
|
|
* Anyone updating a relation's mapping info should take exclusive lock on
|
|
* that rel and hold it until commit. This ensures that there will not be
|
|
* concurrent updates on the same mapping value; but there could easily be
|
|
* concurrent updates on different values in the same file. We cover that
|
|
* by acquiring the RelationMappingLock, re-reading the target file to
|
|
* ensure it's up to date, applying the updates, and writing the data
|
|
* before releasing RelationMappingLock.
|
|
*
|
|
* There is only one RelationMappingLock. In principle we could try to
|
|
* have one per mapping file, but it seems unlikely to be worth the
|
|
* trouble.
|
|
*/
|
|
LWLockAcquire(RelationMappingLock, LW_EXCLUSIVE);
|
|
|
|
/* Be certain we see any other updates just made */
|
|
load_relmap_file(shared);
|
|
|
|
/* Prepare updated data in a local variable */
|
|
if (shared)
|
|
memcpy(&newmap, &shared_map, sizeof(RelMapFile));
|
|
else
|
|
memcpy(&newmap, &local_map, sizeof(RelMapFile));
|
|
|
|
/* Apply the updates to newmap. No new mappings should appear. */
|
|
merge_map_updates(&newmap, updates, false);
|
|
|
|
/* Write out the updated map and do other necessary tasks */
|
|
write_relmap_file(shared, &newmap, true, true, true,
|
|
(shared ? InvalidOid : MyDatabaseId),
|
|
(shared ? GLOBALTABLESPACE_OID : MyDatabaseTableSpace),
|
|
DatabasePath);
|
|
|
|
/* Now we can release the lock */
|
|
LWLockRelease(RelationMappingLock);
|
|
}
|
|
|
|
/*
|
|
* RELMAP resource manager's routines
|
|
*/
|
|
void
|
|
relmap_redo(XLogRecPtr lsn, XLogRecord *record)
|
|
{
|
|
uint8 info = record->xl_info & ~XLR_INFO_MASK;
|
|
|
|
/* Backup blocks are not used in relmap records */
|
|
Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
|
|
|
|
if (info == XLOG_RELMAP_UPDATE)
|
|
{
|
|
xl_relmap_update *xlrec = (xl_relmap_update *) XLogRecGetData(record);
|
|
RelMapFile newmap;
|
|
char *dbpath;
|
|
|
|
if (xlrec->nbytes != sizeof(RelMapFile))
|
|
elog(PANIC, "relmap_redo: wrong size %u in relmap update record",
|
|
xlrec->nbytes);
|
|
memcpy(&newmap, xlrec->data, sizeof(newmap));
|
|
|
|
/* We need to construct the pathname for this database */
|
|
dbpath = GetDatabasePath(xlrec->dbid, xlrec->tsid);
|
|
|
|
/*
|
|
* Write out the new map and send sinval, but of course don't write a
|
|
* new WAL entry. There's no surrounding transaction to tell to
|
|
* preserve files, either.
|
|
*
|
|
* There shouldn't be anyone else updating relmaps during WAL replay,
|
|
* so we don't bother to take the RelationMappingLock. We would need
|
|
* to do so if load_relmap_file needed to interlock against writers.
|
|
*/
|
|
write_relmap_file((xlrec->dbid == InvalidOid), &newmap,
|
|
false, true, false,
|
|
xlrec->dbid, xlrec->tsid, dbpath);
|
|
|
|
pfree(dbpath);
|
|
}
|
|
else
|
|
elog(PANIC, "relmap_redo: unknown op code %u", info);
|
|
}
|
|
|
|
void
|
|
relmap_desc(StringInfo buf, uint8 xl_info, char *rec)
|
|
{
|
|
uint8 info = xl_info & ~XLR_INFO_MASK;
|
|
|
|
if (info == XLOG_RELMAP_UPDATE)
|
|
{
|
|
xl_relmap_update *xlrec = (xl_relmap_update *) rec;
|
|
|
|
appendStringInfo(buf, "update relmap: database %u tablespace %u size %u",
|
|
xlrec->dbid, xlrec->tsid, xlrec->nbytes);
|
|
}
|
|
else
|
|
appendStringInfo(buf, "UNKNOWN");
|
|
}
|