greenplumn appendonly_compaction 源码
greenplumn appendonly_compaction 代码
文件路径：/src/backend/access/appendonly/appendonly_compaction.c
/*------------------------------------------------------------------------------
*
* Code dealing with the compaction of append-only tables.
*
* Compaction is the part of updatable append-only tables that
* is responsible to freeing the space occupied by tuples that have
* been deleted or updated.
*
* The general process is that first all visible tuples of a segment
* file (or a set of segment files) are moved to a different segment file.
* Afterwards in a different transaction that requires AccessExclusiveLocks
* the compacted segment files are dropped and the eof/tupcount/varblock
* information in pg_aoseg_<oid> are reset to 0.
*
* Copyright (c) 2013-Present VMware, Inc. or its affiliates.
*
*
* IDENTIFICATION
* src/backend/access/appendonly/appendonly_compaction.c
*
*------------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/aocs_compaction.h"
#include "access/aomd.h"
#include "access/aosegfiles.h"
#include "access/appendonly_compaction.h"
#include "access/appendonlywriter.h"
#include "access/genam.h"
#include "access/heapam.h"
#include "access/transam.h"
#include "access/tuptoaster.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/pg_am.h"
#include "catalog/pg_appendonly.h"
#include "cdb/cdbappendonlyam.h"
#include "cdb/cdbvars.h"
#include "commands/vacuum.h"
#include "executor/executor.h"
#include "nodes/execnodes.h"
#include "storage/procarray.h"
#include "storage/lmgr.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/relcache.h"
#include "utils/guc.h"
#include "utils/snapmgr.h"
#include "miscadmin.h"
/*
* Drops a segment file.
*
* Actually, we just truncate the segfile to 0 bytes, to reclaim the space.
* Before GPDB 6, we used to remove the file, but with WAL replication, we
* no longer have a convenient function to remove a single segment of a
* relation. An empty file is as almost as good as a non-existent file. If
* the relation is dropped later, the code in mdunlink() will remove all
* segments, including any empty ones we've left behind.
*/
static void
AppendOnlyCompaction_DropSegmentFile(Relation aorel, int segno)
{
char filenamepath[MAXPGPATH];
int32 fileSegNo;
File fd;
Assert(RelationIsAoRows(aorel));
if (Debug_appendonly_print_compaction)
elog(LOG, "Drop segment file: segno %d", segno);
/* Open and truncate the relation segfile */
MakeAOSegmentFileName(aorel, segno, -1, &fileSegNo, filenamepath);
fd = OpenAOSegmentFile(filenamepath, 0);
if (fd >= 0)
{
TruncateAOSegmentFile(fd, aorel, fileSegNo, 0);
CloseAOSegmentFile(fd);
}
else
{
/*
* The file we were about to drop/truncate didn't exist. That shouldn't
* happen, but the end result is what we wanted. Assert so that we will
* find out if this happens, after all, in testing. In production, we'd
* rather keep running.
*/
elog(LOG, "could not truncate segfile %s, because it does not exist", filenamepath);
Assert(false);
}
}
/*
* Calculates the ratio of hidden tuples as a double between 0 and 100
*/
static double
AppendOnlyCompaction_GetHideRatio(int64 hiddenTupcount, int64 totalTupcount)
{
double hideRatio;
if (hiddenTupcount == 0 || totalTupcount == 0)
{
return 0;
}
hideRatio = ((double) hiddenTupcount) / ((double) totalTupcount) * 100.0;
return hideRatio;
}
/*
* Returns true iff the given segment file should be compacted.
*/
bool
AppendOnlyCompaction_ShouldCompact(Relation aoRelation,
int segno,
int64 segmentTotalTupcount,
bool isFull,
Snapshot appendOnlyMetaDataSnapshot)
{
bool result;
AppendOnlyVisimap visiMap;
int64 hiddenTupcount;
double hideRatio;
Oid visimaprelid;
Oid visimapidxid;
Assert(RelationIsAppendOptimized(aoRelation));
GetAppendOnlyEntryAuxOids(aoRelation->rd_id, appendOnlyMetaDataSnapshot,
NULL, NULL, NULL,
&visimaprelid, &visimapidxid);
if (!gp_appendonly_compaction)
{
ereport(LOG,
(errmsg("append-only compaction skipped on relation %s, segment file num %d",
RelationGetRelationName(aoRelation),
segno),
errdetail("Compaction is disabled.")));
/* Disable compaction by global guc. */
return false;
}
AppendOnlyVisimap_Init(&visiMap,
visimaprelid,
visimapidxid,
ShareLock,
appendOnlyMetaDataSnapshot);
hiddenTupcount = AppendOnlyVisimap_GetSegmentFileHiddenTupleCount(
&visiMap, segno);
result = true;
if (isFull && hiddenTupcount > 0)
{
/*
* if it is a full vacuum and there is any obsolete data, do a
* compaction
*/
result = true;
}
else
{
hideRatio = AppendOnlyCompaction_GetHideRatio(hiddenTupcount, segmentTotalTupcount);
if (hideRatio <= gp_appendonly_compaction_threshold || gp_appendonly_compaction_threshold == 0)
{
if (hiddenTupcount > 0)
{
ereportif(Debug_appendonly_print_compaction, LOG,
(errmsg("Append-only compaction skipped on relation %s, segment file num %d, "
"hidden tupcount " INT64_FORMAT ", total tupcount " INT64_FORMAT ", "
"hide ratio %lf%%, threshold %d%%",
RelationGetRelationName(aoRelation),
segno,
hiddenTupcount, segmentTotalTupcount,
hideRatio, gp_appendonly_compaction_threshold)));
ereport(LOG,
(errmsg("Append-only compaction skipped on relation %s, segment file num %d",
RelationGetRelationName(aoRelation),
segno),
errdetail("Ratio of obsolete tuples below threshold (%lf%% vs %d%%)",
hideRatio, gp_appendonly_compaction_threshold)));
}
else
{
ereportif(Debug_appendonly_print_compaction, LOG,
(errmsg("Append-only compaction skipped on relation %s, segment file num %d, "
"hidden tupcount " INT64_FORMAT ", total tupcount " INT64_FORMAT ", "
"hide ratio %lf%%, threshold %d%%",
RelationGetRelationName(aoRelation),
segno,
hiddenTupcount, segmentTotalTupcount,
hideRatio, gp_appendonly_compaction_threshold)));
}
result = false;
}
elogif(Debug_appendonly_print_compaction, LOG,
"Schedule compaction: "
"segno %d, "
"hidden tupcount " INT64_FORMAT ", total tupcount " INT64_FORMAT ", "
"hide ratio %lf%%, threshold %d%%",
segno,
hiddenTupcount, segmentTotalTupcount,
hideRatio, gp_appendonly_compaction_threshold);
}
AppendOnlyVisimap_Finish(&visiMap, ShareLock);
return result;
}
/*
* AppendOnlySegmentFileTruncateToEOF()
*
* Assumes that the segment file lock is already held.
*
* For the segment file is truncates to the eof.
*/
static void
AppendOnlySegmentFileTruncateToEOF(Relation aorel, int segno, int64 segeof)
{
const char *relname = RelationGetRelationName(aorel);
File fd;
int32 fileSegNo;
char filenamepath[MAXPGPATH];
Assert(RelationIsAoRows(aorel));
relname = RelationGetRelationName(aorel);
/* Open and truncate the relation segfile to its eof */
MakeAOSegmentFileName(aorel, segno, -1, &fileSegNo, filenamepath);
elogif(Debug_appendonly_print_compaction, LOG,
"Opening AO relation \"%s.%s\", relation id %u, relfilenode %u (physical segment file #%d, logical EOF " INT64_FORMAT ")",
get_namespace_name(RelationGetNamespace(aorel)),
relname,
aorel->rd_id,
aorel->rd_node.relNode,
segno,
segeof);
fd = OpenAOSegmentFile(filenamepath, segeof);
if (fd >= 0)
{
TruncateAOSegmentFile(fd, aorel, fileSegNo, segeof);
CloseAOSegmentFile(fd);
elogif(Debug_appendonly_print_compaction, LOG,
"Successfully truncated AO ROW relation \"%s.%s\", relation id %u, relfilenode %u (physical segment file #%d, logical EOF " INT64_FORMAT ")",
get_namespace_name(RelationGetNamespace(aorel)),
relname,
aorel->rd_id,
aorel->rd_node.relNode,
segno,
segeof);
}
else
{
elogif(Debug_appendonly_print_compaction, LOG,
"No gp_relation_node entry for AO ROW relation \"%s.%s\", relation id %u, relfilenode %u (physical segment file #%d, logical EOF " INT64_FORMAT ")",
get_namespace_name(RelationGetNamespace(aorel)),
relname,
aorel->rd_id,
aorel->rd_node.relNode,
segno,
segeof);
}
}
static void
AppendOnlyMoveTuple(TupleTableSlot *slot,
MemTupleBinding *mt_bind,
AppendOnlyInsertDesc insertDesc,
ResultRelInfo *resultRelInfo,
EState *estate)
{
MemTuple tuple;
AOTupleId *oldAoTupleId;
AOTupleId newAoTupleId;
Assert(resultRelInfo);
Assert(slot);
Assert(mt_bind);
Assert(estate);
oldAoTupleId = (AOTupleId *) &slot->tts_tid;
/* Extract all the values of the tuple */
slot_getallattrs(slot);
tuple = appendonly_form_memtuple(slot, mt_bind);
appendonly_insert(insertDesc,
tuple,
&newAoTupleId);
slot->tts_tid = *((ItemPointerData *) &newAoTupleId);
/* insert index' tuples if needed */
if (resultRelInfo->ri_NumIndices > 0)
{
ExecInsertIndexTuples(slot,
estate,
false, /* noDupError */
NULL, /* specConflict */
NIL /* arbiterIndexes */);
ResetPerTupleExprContext(estate);
}
appendonly_free_memtuple(tuple);
if (Debug_appendonly_print_compaction)
ereport(DEBUG5,
(errmsg("Compaction: Moved tuple (%d," INT64_FORMAT ") -> (%d," INT64_FORMAT ")",
AOTupleIdGet_segmentFileNum(oldAoTupleId), AOTupleIdGet_rowNum(oldAoTupleId),
AOTupleIdGet_segmentFileNum(&newAoTupleId), AOTupleIdGet_rowNum(&newAoTupleId))));
}
void
AppendOnlyThrowAwayTuple(Relation rel, TupleTableSlot *slot, MemTupleBinding *mt_bind)
{
int i;
int numAttrs;
MemTuple tuple;
TupleDesc tupleDesc;
AOTupleId *aoTupleId;
Datum toast_values[MaxHeapAttributeNumber];
bool toast_isnull[MaxHeapAttributeNumber];
Assert(slot);
aoTupleId = (AOTupleId *) &slot->tts_tid;
/* Extract all the values of the tuple */
slot_getallattrs(slot);
tuple = appendonly_form_memtuple(slot, mt_bind);
tupleDesc = rel->rd_att;
numAttrs = tupleDesc->natts;
Assert(numAttrs <= MaxHeapAttributeNumber);
memtuple_deform((MemTuple) tuple, mt_bind, toast_values, toast_isnull);
/* loop through all attributes, delete external stored values */
for (i = 0; i < numAttrs; i++)
{
if (TupleDescAttr(tupleDesc, i)->attlen == -1)
{
Datum value = toast_values[i];
if (toast_isnull[i])
continue;
else if (VARATT_IS_EXTERNAL_ONDISK(PointerGetDatum(value)))
toast_delete_datum(rel, value, false);
}
}
appendonly_free_memtuple(tuple);
if (Debug_appendonly_print_compaction)
ereport(DEBUG5,
(errmsg("Compaction: Throw away tuple (%d," INT64_FORMAT ")",
AOTupleIdGet_segmentFileNum(aoTupleId),
AOTupleIdGet_rowNum(aoTupleId))));
}
/*
* Assumes that the segment file lock is already held.
* Assumes that the segment file should be compacted.
*
*/
static void
AppendOnlySegmentFileFullCompaction(Relation aorel,
AppendOnlyInsertDesc insertDesc,
FileSegInfo *fsinfo,
Snapshot appendOnlyMetaDataSnapshot)
{
const char *relname;
AppendOnlyVisimap visiMap;
AppendOnlyScanDesc scanDesc;
TupleDesc tupDesc;
TupleTableSlot *slot;
MemTupleBinding *mt_bind;
int compact_segno;
int64 movedTupleCount = 0;
ResultRelInfo *resultRelInfo;
EState *estate;
AOTupleId *aoTupleId;
int64 tupleCount = 0;
int64 tuplePerPage = INT_MAX;
Oid visimaprelid;
Oid visimapidxid;
Oid blkdirrelid;
Assert(Gp_role == GP_ROLE_EXECUTE || Gp_role == GP_ROLE_UTILITY);
Assert(RelationIsAoRows(aorel));
Assert(insertDesc);
compact_segno = fsinfo->segno;
if (fsinfo->varblockcount > 0)
{
tuplePerPage = fsinfo->total_tupcount / fsinfo->varblockcount;
}
relname = RelationGetRelationName(aorel);
GetAppendOnlyEntryAuxOids(aorel->rd_id, appendOnlyMetaDataSnapshot,
NULL, &blkdirrelid, NULL,
&visimaprelid, &visimapidxid);
AppendOnlyVisimap_Init(&visiMap,
visimaprelid,
visimapidxid,
ShareUpdateExclusiveLock,
appendOnlyMetaDataSnapshot);
if (Debug_appendonly_print_compaction)
elog(LOG, "Compact AO segno %d, relation %s, insert segno %d",
compact_segno, relname, insertDesc->storageWrite.segmentFileNum);
/*
* Todo: We need to limit the scan to one file and we need to avoid to
* lock the file again.
*
* We use SnapshotAny to get visible and invisible tuples.
*/
scanDesc = appendonly_beginrangescan(aorel,
SnapshotAny, appendOnlyMetaDataSnapshot,
&compact_segno, 1, 0, NULL);
tupDesc = RelationGetDescr(aorel);
slot = MakeSingleTupleTableSlot(tupDesc, &TTSOpsVirtual);
slot->tts_tableOid = RelationGetRelid(aorel);
mt_bind = create_memtuple_binding(tupDesc);
/*
* We need a ResultRelInfo and an EState so we can use the regular
* executor's index-entry-making machinery.
*/
estate = CreateExecutorState();
resultRelInfo = makeNode(ResultRelInfo);
resultRelInfo->ri_RangeTableIndex = 1; /* dummy */
resultRelInfo->ri_RelationDesc = aorel;
resultRelInfo->ri_TrigDesc = NULL; /* we don't fire triggers */
ExecOpenIndices(resultRelInfo, false);
estate->es_result_relations = resultRelInfo;
estate->es_num_result_relations = 1;
estate->es_result_relation_info = resultRelInfo;
/*
* Go through all visible tuples and move them to a new segfile.
*/
while (appendonly_getnextslot(&scanDesc->rs_base, ForwardScanDirection, slot))
{
/* Check interrupts as this may take time. */
CHECK_FOR_INTERRUPTS();
aoTupleId = (AOTupleId *) &slot->tts_tid;
if (AppendOnlyVisimap_IsVisible(&scanDesc->visibilityMap, aoTupleId))
{
AppendOnlyMoveTuple(slot,
mt_bind,
insertDesc,
resultRelInfo,
estate);
movedTupleCount++;
}
else
{
/* Tuple is invisible and needs to be dropped */
AppendOnlyThrowAwayTuple(aorel, slot, mt_bind);
}
/*
* Check for vacuum delay point after approximately a var block
*/
tupleCount++;
if (VacuumCostActive && tupleCount % tuplePerPage == 0)
{
vacuum_delay_point();
}
}
MarkFileSegInfoAwaitingDrop(aorel, compact_segno);
AppendOnlyVisimap_DeleteSegmentFile(&visiMap, compact_segno);
/* Delete all mini pages of the segment files if block directory exists */
if (OidIsValid(blkdirrelid))
{
AppendOnlyBlockDirectory_DeleteSegmentFile(aorel,
appendOnlyMetaDataSnapshot,
compact_segno,
0);
}
if (Debug_appendonly_print_compaction)
elog(LOG, "Finished compaction: AO segfile %d, relation %s, moved tuple count " INT64_FORMAT,
compact_segno, relname, movedTupleCount);
AppendOnlyVisimap_Finish(&visiMap, NoLock);
ExecCloseIndices(resultRelInfo);
FreeExecutorState(estate);
ExecDropSingleTupleTableSlot(slot);
destroy_memtuple_binding(mt_bind);
appendonly_endscan(&scanDesc->rs_base);
}
/*
* Collect AWAITING_DROP segments.
*
* Acquire AccessShareLock with cutoff_xid to scan and collect dead
* segments.
*/
Bitmapset *
AppendOptimizedCollectDeadSegments(Relation aorel)
{
Relation pg_aoseg_rel;
TupleDesc pg_aoseg_dsc;
SysScanDesc aoscan;
HeapTuple tuple;
Snapshot appendOnlyMetaDataSnapshot = RegisterSnapshot(GetCatalogSnapshot(InvalidOid));
TransactionId cutoff_xid = InvalidTransactionId;
Oid segrelid;
Bitmapset *dead_segs = NULL;
Assert(RelationIsAppendOptimized(aorel));
GetAppendOnlyEntryAuxOids(aorel->rd_id, appendOnlyMetaDataSnapshot,
&segrelid, NULL, NULL, NULL, NULL);
pg_aoseg_rel = heap_open(segrelid, AccessShareLock);
pg_aoseg_dsc = RelationGetDescr(pg_aoseg_rel);
aoscan = systable_beginscan(pg_aoseg_rel, InvalidOid, false, appendOnlyMetaDataSnapshot, 0, NULL);
while ((tuple = systable_getnext(aoscan)) != NULL)
{
bool visible_to_all;
int segno;
int16 state;
bool isNull;
TransactionId xmin;
if (RelationIsAoRows(aorel))
{
segno = DatumGetInt32(fastgetattr(tuple,
Anum_pg_aoseg_segno,
pg_aoseg_dsc, &isNull));
Assert(!isNull);
state = DatumGetInt16(fastgetattr(tuple,
Anum_pg_aoseg_state,
pg_aoseg_dsc, &isNull));
Assert(!isNull);
}
else
{
segno = DatumGetInt32(fastgetattr(tuple,
Anum_pg_aocs_segno,
pg_aoseg_dsc, &isNull));
Assert(!isNull);
state = DatumGetInt16(fastgetattr(tuple,
Anum_pg_aocs_state,
pg_aoseg_dsc, &isNull));
Assert(!isNull);
}
if (state != AOSEG_STATE_AWAITING_DROP)
continue;
/*
* Cutoff XID Screening
*
* It's in awaiting-drop state, but does everyone see it that way?
*
* Compare the tuple's xmin with the oldest-xmin horizon. We don't bother
* checking the xmax; we never update or lock awaiting-drop tuples, so it
* should not be set. Even if the tuple was update, presumably an AO
* segment that's in awaiting-drop state won't be resurrected, so even if
* someone updates or locks the tuple, it's still safe to drop.
*
* We don't need to acquire AccessExclusiveLock any longer because we only
* scan pg_aoseg to collect dead segments but no truncaste happens here.
* Considering the following two cases:
*
* a) When there was a reader accessing a segment file which was changed to
* AWAITING_DROP in later VACUUM compaction, the reader's xid should be earlier
* than this tuple's xmin hence would set visible_to_all to false. Then the
* AWAITING_DROP segment file wouldn't be dropped in this VACUUM cleanup and
* the earlier reader could still be able to access old tuples.
*
* b) Continue above, so there was a segment file in AWAITING_DROP state, the
* subsequent transactions can't see that hence it wouldn't be touched until
* next VACUUM is arrived. Therefore no later transaction's xid could be earlier
* than this dead segment tuple's xmin hence it would be true on visible_to_all.
* Then the corresponding dead segment file could be dropped later at that time.
*/
xmin = HeapTupleHeaderGetXmin(tuple->t_data);
if (xmin == FrozenTransactionId)
visible_to_all = true;
else
{
if (cutoff_xid == InvalidTransactionId)
cutoff_xid = GetOldestXmin(NULL, PROCARRAY_FLAGS_VACUUM);
visible_to_all = TransactionIdPrecedes(xmin, cutoff_xid);
}
if (!visible_to_all)
continue;
/* collect dead segnos for dropping */
dead_segs = bms_add_member(dead_segs, segno);
}
systable_endscan(aoscan);
heap_close(pg_aoseg_rel, AccessShareLock);
UnregisterSnapshot(appendOnlyMetaDataSnapshot);
return dead_segs;
}
/*
* Drop AWAITING_DROP segments.
*
* Callers should guarantee that the segfile is no longer needed by any
* running transaction. It is not necessary to hold a lock on the segfile
* row, though.
*/
static inline void
AppendOptimizedDropDeadSegment(Relation aorel, int segno)
{
if (RelationIsAoRows(aorel))
{
AppendOnlyCompaction_DropSegmentFile(aorel, segno);
ClearFileSegInfo(aorel, segno);
}
else
{
AOCSCompaction_DropSegmentFile(aorel, segno);
ClearAOCSFileSegInfo(aorel, segno);
}
}
void
AppendOptimizedDropDeadSegments(Relation aorel, Bitmapset *segnos)
{
int segno;
/*
* drop segments in batch with concurrent-safety
*/
LockRelationForExtension(aorel, ExclusiveLock);
segno = -1;
while ((segno = bms_next_member(segnos, segno)) >= 0)
AppendOptimizedDropDeadSegment(aorel, segno);
UnlockRelationForExtension(aorel, ExclusiveLock);
}
/*
* Truncates each segment file in the AO relation to its EOF.
* If we cannot get a lock on the segment file (because e.g. a concurrent insert)
* the segment file is skipped.
*/
void
AppendOptimizedTruncateToEOF(Relation aorel)
{
const char *relname;
Relation pg_aoseg_rel;
TupleDesc pg_aoseg_dsc;
SysScanDesc aoscan;
HeapTuple tuple;
Snapshot appendOnlyMetaDataSnapshot = RegisterSnapshot(GetCatalogSnapshot(InvalidOid));
Oid segrelid;
Assert(RelationIsAppendOptimized(aorel));
relname = RelationGetRelationName(aorel);
/*
* The algorithm below for choosing a target segment is not concurrent-safe.
* Grab a lock to serialize.
*/
LockRelationForExtension(aorel, ExclusiveLock);
GetAppendOnlyEntryAuxOids(aorel->rd_id, appendOnlyMetaDataSnapshot,
&segrelid, NULL, NULL, NULL, NULL);
pg_aoseg_rel = heap_open(segrelid, AccessShareLock);
pg_aoseg_dsc = RelationGetDescr(pg_aoseg_rel);
aoscan = systable_beginscan(pg_aoseg_rel, InvalidOid, false, appendOnlyMetaDataSnapshot, 0, NULL);
while ((tuple = systable_getnext(aoscan)) != NULL)
{
int segno;
bool isNull;
if (RelationIsAoRows(aorel))
{
segno = DatumGetInt32(fastgetattr(tuple,
Anum_pg_aoseg_segno,
pg_aoseg_dsc, &isNull));
Assert(!isNull);
}
else
{
segno = DatumGetInt32(fastgetattr(tuple,
Anum_pg_aocs_segno,
pg_aoseg_dsc, &isNull));
Assert(!isNull);
}
/*
* Is anyone writing to this segfile? Readers are OK, because they won't
* try to read beyond the EOF as stated in the pg_aoseg entry
*/
if (!pg_aoseg_tuple_could_be_updated(pg_aoseg_rel, tuple))
continue;
if (RelationIsAoRows(aorel))
{
int64 segeof;
segeof = DatumGetInt64(fastgetattr(tuple,
Anum_pg_aoseg_eof,
pg_aoseg_dsc, &isNull));
Assert(!isNull);
AppendOnlySegmentFileTruncateToEOF(aorel, segno, segeof);
}
else
{
Datum d = fastgetattr(tuple,
Anum_pg_aocs_vpinfo,
pg_aoseg_dsc, &isNull);
AOCSVPInfo *vpinfo = (AOCSVPInfo *) PG_DETOAST_DATUM(d);
AOCSSegmentFileTruncateToEOF(aorel, segno, vpinfo);
if (DatumGetPointer(d) != (Pointer) vpinfo)
pfree(vpinfo);
}
}
systable_endscan(aoscan);
UnlockRelationForExtension(aorel, ExclusiveLock);
heap_close(pg_aoseg_rel, AccessShareLock);
UnregisterSnapshot(appendOnlyMetaDataSnapshot);
}
/*
* Performs a compaction of an append-only relation.
*
* The compaction segment file should be marked as in-use/in-compaction in
* the appendonlywriter.c code.
*
* On exit, *insert_segno will be set to the the segment that was used as the
* insertion target. The segfiles listed in 'avoid_segnos' will not be used
* for insertion.
*
* The caller is required to hold either an AccessExclusiveLock (vacuum full)
* or a ShareLock on the relation.
*/
void
AppendOnlyCompact(Relation aorel,
int compaction_segno,
int *insert_segno,
bool isFull,
List *avoid_segnos)
{
const char *relname;
AppendOnlyInsertDesc insertDesc = NULL;
FileSegInfo *fsinfo;
Snapshot appendOnlyMetaDataSnapshot = RegisterSnapshot(GetCatalogSnapshot(InvalidOid));
Assert(RelationIsAoRows(aorel));
Assert(Gp_role == GP_ROLE_EXECUTE || Gp_role == GP_ROLE_UTILITY);
relname = RelationGetRelationName(aorel);
/* Fetch under the write lock to get latest committed eof. */
fsinfo = GetFileSegInfo(aorel, appendOnlyMetaDataSnapshot, compaction_segno, true);
if (AppendOnlyCompaction_ShouldCompact(aorel,
fsinfo->segno, fsinfo->total_tupcount, isFull,
appendOnlyMetaDataSnapshot))
{
if (*insert_segno == -1)
{
/* get the insertion segment on first call. */
*insert_segno = ChooseSegnoForCompactionWrite(aorel, avoid_segnos);
}
if (*insert_segno != -1)
{
insertDesc = appendonly_insert_init(aorel, *insert_segno);
AppendOnlySegmentFileFullCompaction(aorel,
insertDesc,
fsinfo,
appendOnlyMetaDataSnapshot);
insertDesc->skipModCountIncrement = true;
appendonly_insert_finish(insertDesc);
}
else
{
/* Could not find a target segment. Give up */
ereport(WARNING,
(errmsg("could not find a free segment file to use for compacting segfile %d of relation %s",
compaction_segno, RelationGetRelationName(aorel))));
}
}
pfree(fsinfo);
UnregisterSnapshot(appendOnlyMetaDataSnapshot);
}
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