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Handle aborted writes properly when scanning a columnar table (#5244) 

If it is certain that we will not use any `parallel_worker`s for a columnar table,
then stripe entries inserted by aborted transactions become visible to
`SnapshotAny` and that causes `REINDEX` to fail by throwing a duplicate key
error.

To fix that:
* consider three states for a stripe write operation:
   "flushed", "aborted", or "in-progress",
* make sure to have a clear separation between them, and
* act according to those three states when reading from a columnar table
pull/5245/head
Onur Tirtir 2021-09-08 13:26:11 +03:00 committed by GitHub
parent 5dc619162d
commit 5825c44d5f
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 169 additions and 62 deletions
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162
src/backend/columnar/columnar_metadata.c
View File

@ -51,6 +51,7 @@
#include "port.h"
#include "storage/fd.h"
#include "storage/lmgr.h"
#include "storage/procarray.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
@ -91,7 +92,8 @@ static void GetHighestUsedAddressAndId(uint64 storageId,
static StripeMetadata * UpdateStripeMetadataRow(uint64 storageId, uint64 stripeId,
bool *update, Datum *newValues);
static List * ReadDataFileStripeList(uint64 storageId, Snapshot snapshot);
static StripeMetadata * BuildStripeMetadata(Datum *datumArray);
static StripeMetadata * BuildStripeMetadata(Relation columnarStripes,
HeapTuple heapTuple);
static uint32 * ReadChunkGroupRowCounts(uint64 storageId, uint64 stripe, uint32
chunkGroupCount, Snapshot snapshot);
static Oid ColumnarStorageIdSequenceRelationId(void);
@ -701,19 +703,23 @@ FindStripeWithMatchingFirstRowNumber(Relation relation, uint64 rowNumber,
/*
* StripeIsFlushed returns true if stripe with stripeMetadata is flushed to
* disk.
* StripeWriteState returns write state of given stripe.
*/
bool
StripeIsFlushed(StripeMetadata *stripeMetadata)
StripeWriteStateEnum
StripeWriteState(StripeMetadata *stripeMetadata)
{
/*
* We insert dummy stripe metadata entry when inserting the first row.
* For this reason, rowCount being equal to 0 cannot mean a valid stripe
* with 0 rows but a stripe that is not flushed to disk, probably because
* of an aborted xact.
*/
return stripeMetadata->rowCount > 0;
if (stripeMetadata->aborted)
{
return STRIPE_WRITE_ABORTED;
}
else if (stripeMetadata->rowCount > 0)
{
return STRIPE_WRITE_FLUSHED;
}
else
{
return STRIPE_WRITE_IN_PROGRESS;
}
}
@ -783,13 +789,7 @@ StripeMetadataLookupRowNumber(Relation relation, uint64 rowNumber, Snapshot snap
HeapTuple heapTuple = systable_getnext_ordered(scanDescriptor, scanDirection);
if (HeapTupleIsValid(heapTuple))
{
TupleDesc tupleDescriptor = RelationGetDescr(columnarStripes);
Datum datumArray[Natts_columnar_stripe];
bool isNullArray[Natts_columnar_stripe];
heap_deform_tuple(heapTuple, tupleDescriptor, datumArray, isNullArray);
foundStripeMetadata = BuildStripeMetadata(datumArray);
CheckStripeMetadataConsistency(foundStripeMetadata);
foundStripeMetadata = BuildStripeMetadata(columnarStripes, heapTuple);
}
systable_endscan_ordered(scanDescriptor);
@ -801,30 +801,79 @@ StripeMetadataLookupRowNumber(Relation relation, uint64 rowNumber, Snapshot snap
/*
* CheckStripeMetadataConsistency errors out if given StripeMetadata object
* belongs to an un-flushed stripe but some fields of it contradicts with
* this fact.
* CheckStripeMetadataConsistency first decides if stripe write operation for
* given stripe is "flushed", "aborted" or "in-progress", then errors out if
* its metadata entry contradicts with this fact.
*
* Checks performed here are just to catch bugs, so it is encouraged to call
* this function whenever a StripeMetadata object is built from an heap tuple
* of columnar.stripe. Currently, BuildStripeMetadata is the only function
* that does this.
*/
static void
CheckStripeMetadataConsistency(StripeMetadata *stripeMetadata)
{
if (StripeIsFlushed(stripeMetadata))
{
return;
}
bool stripeLooksInProgress =
stripeMetadata->rowCount == 0 && stripeMetadata->chunkCount == 0 &&
stripeMetadata->fileOffset == ColumnarInvalidLogicalOffset &&
stripeMetadata->dataLength == 0;
if (stripeMetadata->rowCount > 0 || stripeMetadata->chunkCount > 0 ||
stripeMetadata->fileOffset != ColumnarInvalidLogicalOffset ||
stripeMetadata->dataLength > 0)
/*
* Even if stripe is flushed, fileOffset and dataLength might be equal
* to 0 for zero column tables, but those two should still be consistent
* with respect to each other.
*/
bool stripeLooksFlushed =
stripeMetadata->rowCount > 0 && stripeMetadata->chunkCount > 0 &&
((stripeMetadata->fileOffset != ColumnarInvalidLogicalOffset &&
stripeMetadata->dataLength > 0) ||
(stripeMetadata->fileOffset == ColumnarInvalidLogicalOffset &&
stripeMetadata->dataLength == 0));
switch (StripeWriteState(stripeMetadata))
{
/*
* If stripe was not flushed to disk, then values of given four
* fields should match the columns inserted by
* InsertEmptyStripeMetadataRow.
*/
ereport(ERROR, (errmsg("unexpected stripe state, stripe with id="
UINT64_FORMAT " was not flushed properly",
stripeMetadata->id)));
case STRIPE_WRITE_FLUSHED:
{
/*
* If stripe was flushed to disk, then we expect stripe to store
* at least one tuple.
*/
if (stripeLooksFlushed)
{
break;
}
}
case STRIPE_WRITE_IN_PROGRESS:
{
/*
* If stripe was not flushed to disk, then values of given four
* fields should match the columns inserted by
* InsertEmptyStripeMetadataRow.
*/
if (stripeLooksInProgress)
{
break;
}
}
case STRIPE_WRITE_ABORTED:
{
/*
* Stripe metadata entry for an aborted write can be complete or
* incomplete. We might have aborted the transaction before or after
* inserting into stripe metadata.
*/
if (stripeLooksInProgress || stripeLooksFlushed)
{
break;
}
}
default:
ereport(ERROR, (errmsg("unexpected stripe state, stripe metadata "
"entry for stripe with id=" UINT64_FORMAT
" is not consistent", stripeMetadata->id)));
}
}
@ -853,12 +902,7 @@ FindStripeWithHighestRowNumber(Relation relation, Snapshot snapshot)
HeapTuple heapTuple = systable_getnext_ordered(scanDescriptor, BackwardScanDirection);
if (HeapTupleIsValid(heapTuple))
{
TupleDesc tupleDescriptor = RelationGetDescr(columnarStripes);
Datum datumArray[Natts_columnar_stripe];
bool isNullArray[Natts_columnar_stripe];
heap_deform_tuple(heapTuple, tupleDescriptor, datumArray, isNullArray);
stripeWithHighestRowNumber = BuildStripeMetadata(datumArray);
stripeWithHighestRowNumber = BuildStripeMetadata(columnarStripes, heapTuple);
}
systable_endscan_ordered(scanDescriptor);
@ -1147,6 +1191,9 @@ UpdateStripeMetadataRow(uint64 storageId, uint64 stripeId, bool *update,
heap_inplace_update(columnarStripes, modifiedTuple);
StripeMetadata *modifiedStripeMetadata = BuildStripeMetadata(columnarStripes,
modifiedTuple);
CommandCounterIncrement();
systable_endscan_ordered(scanDescriptor);
@ -1154,10 +1201,7 @@ UpdateStripeMetadataRow(uint64 storageId, uint64 stripeId, bool *update,
table_close(columnarStripes, AccessShareLock);
/* return StripeMetadata object built from modified tuple */
Datum datumArray[Natts_columnar_stripe];
bool isNullArray[Natts_columnar_stripe];
heap_deform_tuple(modifiedTuple, tupleDescriptor, datumArray, isNullArray);
return BuildStripeMetadata(datumArray);
return modifiedStripeMetadata;
}
@ -1180,7 +1224,6 @@ ReadDataFileStripeList(uint64 storageId, Snapshot snapshot)
Relation columnarStripes = table_open(columnarStripesOid, AccessShareLock);
Relation index = index_open(ColumnarStripeFirstRowNumberIndexRelationId(),
AccessShareLock);
TupleDesc tupleDescriptor = RelationGetDescr(columnarStripes);
SysScanDesc scanDescriptor = systable_beginscan_ordered(columnarStripes, index,
snapshot, 1,
@ -1189,11 +1232,7 @@ ReadDataFileStripeList(uint64 storageId, Snapshot snapshot)
while (HeapTupleIsValid(heapTuple = systable_getnext_ordered(scanDescriptor,
ForwardScanDirection)))
{
Datum datumArray[Natts_columnar_stripe];
bool isNullArray[Natts_columnar_stripe];
heap_deform_tuple(heapTuple, tupleDescriptor, datumArray, isNullArray);
StripeMetadata *stripeMetadata = BuildStripeMetadata(datumArray);
StripeMetadata *stripeMetadata = BuildStripeMetadata(columnarStripes, heapTuple);
stripeMetadataList = lappend(stripeMetadataList, stripeMetadata);
}
@ -1206,11 +1245,18 @@ ReadDataFileStripeList(uint64 storageId, Snapshot snapshot)
/*
* BuildStripeMetadata builds a StripeMetadata object from given datumArray.
* BuildStripeMetadata builds a StripeMetadata object from given heap tuple.
*/
static StripeMetadata *
BuildStripeMetadata(Datum *datumArray)
BuildStripeMetadata(Relation columnarStripes, HeapTuple heapTuple)
{
Assert(RelationGetRelid(columnarStripes) == ColumnarStripeRelationId());
Datum datumArray[Natts_columnar_stripe];
bool isNullArray[Natts_columnar_stripe];
heap_deform_tuple(heapTuple, RelationGetDescr(columnarStripes),
datumArray, isNullArray);
StripeMetadata *stripeMetadata = palloc0(sizeof(StripeMetadata));
stripeMetadata->id = DatumGetInt64(datumArray[Anum_columnar_stripe_stripe - 1]);
stripeMetadata->fileOffset = DatumGetInt64(
@ -1227,6 +1273,12 @@ BuildStripeMetadata(Datum *datumArray)
datumArray[Anum_columnar_stripe_row_count - 1]);
stripeMetadata->firstRowNumber = DatumGetUInt64(
datumArray[Anum_columnar_stripe_first_row_number - 1]);
TransactionId entryXmin = HeapTupleHeaderGetXmin(heapTuple->t_data);
stripeMetadata->aborted = TransactionIdDidAbort(entryXmin);
CheckStripeMetadataConsistency(stripeMetadata);
return stripeMetadata;
}

6
src/backend/columnar/columnar_reader.c
View File

@ -288,7 +288,7 @@ ColumnarReadRowByRowNumber(ColumnarReadState *readState,
return false;
}
if (!StripeIsFlushed(stripeMetadata))
if (StripeWriteState(stripeMetadata) != STRIPE_WRITE_FLUSHED)
{
/*
* Callers are expected to skip stripes that are not flushed to
@ -582,7 +582,7 @@ AdvanceStripeRead(ColumnarReadState *readState)
readState->snapshot);
if (readState->currentStripeMetadata &&
!StripeIsFlushed(readState->currentStripeMetadata) &&
StripeWriteState(readState->currentStripeMetadata) != STRIPE_WRITE_FLUSHED &&
!SnapshotMightSeeUnflushedStripes(readState->snapshot))
{
/*
@ -596,7 +596,7 @@ AdvanceStripeRead(ColumnarReadState *readState)
}
while (readState->currentStripeMetadata &&
!StripeIsFlushed(readState->currentStripeMetadata))
StripeWriteState(readState->currentStripeMetadata) != STRIPE_WRITE_FLUSHED)
{
readState->currentStripeMetadata =
FindNextStripeByRowNumber(readState->relation,

20
src/backend/columnar/columnar_tableam.c
View File

@ -562,7 +562,8 @@ columnar_index_fetch_tuple(struct IndexFetchTableData *sscan,
return false;
}
if (StripeIsFlushed(stripeMetadata) &&
StripeWriteStateEnum stripeWriteState = StripeWriteState(stripeMetadata);
if (stripeWriteState == STRIPE_WRITE_FLUSHED &&
!ColumnarReadRowByRowNumber(scan->cs_readState, rowNumber,
slot->tts_values, slot->tts_isnull))
{
@ -573,8 +574,7 @@ columnar_index_fetch_tuple(struct IndexFetchTableData *sscan,
*/
return false;
}
if (!StripeIsFlushed(stripeMetadata))
else if (stripeWriteState == STRIPE_WRITE_ABORTED)
{
/*
* We only expect to see un-flushed stripes when checking against
@ -582,6 +582,12 @@ columnar_index_fetch_tuple(struct IndexFetchTableData *sscan,
* snapshot to index_fetch_tuple callback.
*/
Assert(snapshot->snapshot_type == SNAPSHOT_DIRTY);
return false;
}
else if (stripeWriteState == STRIPE_WRITE_IN_PROGRESS)
{
/* similar to aborted writes .. */
Assert(snapshot->snapshot_type == SNAPSHOT_DIRTY);
/*
* Stripe that "might" contain the tuple with rowNumber is not
@ -593,6 +599,14 @@ columnar_index_fetch_tuple(struct IndexFetchTableData *sscan,
*/
memset(slot->tts_isnull, true, slot->tts_nvalid);
}
else
{
/*
* At this point, we certainly know that stripe is flushed and
* ColumnarReadRowByRowNumber successfully filled the tupleslot.
*/
Assert(stripeWriteState == STRIPE_WRITE_FLUSHED);
}
slot->tts_tableOid = RelationGetRelid(columnarRelation);
slot->tts_tid = *tid;

23
src/include/columnar/columnar.h
View File

@ -179,6 +179,27 @@ typedef struct StripeBuffers
} StripeBuffers;
/* return value of StripeWriteState to decide stripe write state */
typedef enum StripeWriteStateEnum
{
/* stripe write is flushed to disk, so it's readable */
STRIPE_WRITE_FLUSHED,
/*
* Writer transaction did abort either before inserting into
* columnar.stripe or after.
*/
STRIPE_WRITE_ABORTED,
/*
* Writer transaction is still in-progress. Note that it is not certain
* if it is being written by current backend's current transaction or
* another backend.
*/
STRIPE_WRITE_IN_PROGRESS
} StripeWriteStateEnum;
/* ColumnarReadState represents state of a columnar scan. */
struct ColumnarReadState;
typedef struct ColumnarReadState ColumnarReadState;
@ -268,7 +289,7 @@ extern StripeMetadata * FindStripeByRowNumber(Relation relation, uint64 rowNumbe
extern StripeMetadata * FindStripeWithMatchingFirstRowNumber(Relation relation,
uint64 rowNumber,
Snapshot snapshot);
extern bool StripeIsFlushed(StripeMetadata *stripeMetadata);
extern StripeWriteStateEnum StripeWriteState(StripeMetadata *stripeMetadata);
extern uint64 StripeGetHighestRowNumber(StripeMetadata *stripeMetadata);
extern StripeMetadata * FindStripeWithHighestRowNumber(Relation relation,
Snapshot snapshot);

3
src/include/columnar/columnar_metadata.h
View File

@ -26,6 +26,9 @@ typedef struct StripeMetadata
uint64 rowCount;
uint64 id;
uint64 firstRowNumber;
/* see StripeWriteState */
bool aborted;
} StripeMetadata;
/*

8
src/test/regress/expected/columnar_indexes.out
View File

@ -542,5 +542,13 @@ SELECT sum(a)>-1 FROM revisit_same_cgroup WHERE b = '1';
t
(1 row)
CREATE TABLE aborted_write_test (a INT PRIMARY KEY) USING columnar;
ALTER TABLE aborted_write_test SET (parallel_workers = 0);
INSERT INTO aborted_write_test VALUES (16999);
INSERT INTO aborted_write_test VALUES (16999);
ERROR: duplicate key value violates unique constraint "aborted_write_test_pkey"
DETAIL: Key (a)=(16999) already exists.
-- since second INSERT already failed, should not throw a "duplicate key" error
REINDEX TABLE aborted_write_test;
SET client_min_messages TO WARNING;
DROP SCHEMA columnar_indexes CASCADE;

9
src/test/regress/sql/columnar_indexes.sql
View File

@ -397,5 +397,14 @@ INSERT INTO revisit_same_cgroup SELECT random()*500, (random()*500)::INT::TEXT F
SELECT sum(a)>-1 FROM revisit_same_cgroup WHERE b = '1';
CREATE TABLE aborted_write_test (a INT PRIMARY KEY) USING columnar;
ALTER TABLE aborted_write_test SET (parallel_workers = 0);
INSERT INTO aborted_write_test VALUES (16999);
INSERT INTO aborted_write_test VALUES (16999);
-- since second INSERT already failed, should not throw a "duplicate key" error
REINDEX TABLE aborted_write_test;
SET client_min_messages TO WARNING;
DROP SCHEMA columnar_indexes CASCADE;