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TOAST needs to do at least minimal time-qual checking in order not to
mess up after an aborted VACUUM FULL, per today's pghackers discussion. Add a suitable HeapTupleSatisfiesToast routine. Remove useless special- case test in HeapTupleSatisfiesVisibility macro for xmax = BootstrapTransactionId; perhaps that was needed at one time, but it's a waste of cycles now, not to mention actively wrong for SnapshotAny. Along the way, add some much-needed comments to tqual.c, and simplify toast_fetch_datum, which no longer needs to assume it may see chunks out-of-order.
This commit is contained in:
Tom Lane
parent
0f2d949c1e
commit
cf97080fa4
@ -4,11 +4,11 @@
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* Support routines for external and compressed storage of
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* variable size attributes.
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*
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* Copyright (c) 2000, PostgreSQL Global Development Group
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* Copyright (c) 2000-2002, PostgreSQL Global Development Group
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.26 2001/11/05 17:46:23 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.27 2002/01/16 20:29:01 tgl Exp $
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*
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*
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* INTERFACE ROUTINES
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@ -921,7 +921,7 @@ toast_delete_datum(Relation rel, Datum value)
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while ((indexRes = index_getnext(toastscan, ForwardScanDirection)) != NULL)
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{
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toasttup.t_self = indexRes->heap_iptr;
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heap_fetch(toastrel, SnapshotAny, &toasttup, &buffer, toastscan);
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heap_fetch(toastrel, SnapshotToast, &toasttup, &buffer, toastscan);
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pfree(indexRes);
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if (!toasttup.t_data)
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@ -963,26 +963,18 @@ toast_fetch_datum(varattrib *attr)
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TupleDesc toasttupDesc;
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RetrieveIndexResult indexRes;
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Buffer buffer;
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varattrib *result;
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int32 ressize;
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int32 residx;
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int numchunks;
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int32 residx,
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nextidx;
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int32 numchunks;
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Pointer chunk;
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bool isnull;
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int32 chunksize;
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char *chunks_found;
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char *chunks_expected;
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ressize = attr->va_content.va_external.va_extsize;
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numchunks = ((ressize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
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chunks_found = palloc(numchunks);
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chunks_expected = palloc(numchunks);
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memset(chunks_found, 0, numchunks);
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memset(chunks_expected, 1, numchunks);
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result = (varattrib *) palloc(ressize + VARHDRSZ);
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VARATT_SIZEP(result) = ressize + VARHDRSZ;
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if (VARATT_IS_COMPRESSED(attr))
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@ -1008,13 +1000,17 @@ toast_fetch_datum(varattrib *attr)
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/*
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* Read the chunks by index
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*
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* Note we will not necessarily see the chunks in sequence-number order.
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* Note that because the index is actually on (valueid, chunkidx)
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* we will see the chunks in chunkidx order, even though we didn't
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* explicitly ask for it.
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*/
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nextidx = 0;
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toastscan = index_beginscan(toastidx, false, 1, &toastkey);
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while ((indexRes = index_getnext(toastscan, ForwardScanDirection)) != NULL)
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{
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toasttup.t_self = indexRes->heap_iptr;
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heap_fetch(toastrel, SnapshotAny, &toasttup, &buffer, toastscan);
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heap_fetch(toastrel, SnapshotToast, &toasttup, &buffer, toastscan);
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pfree(indexRes);
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if (toasttup.t_data == NULL)
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@ -1033,9 +1029,9 @@ toast_fetch_datum(varattrib *attr)
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/*
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* Some checks on the data we've found
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*/
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if (residx < 0 || residx >= numchunks)
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elog(ERROR, "unexpected chunk number %d for toast value %u",
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residx,
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if (residx != nextidx)
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elog(ERROR, "unexpected chunk number %d (expected %d) for toast value %u",
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residx, nextidx,
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attr->va_content.va_external.va_valueid);
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if (residx < numchunks - 1)
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{
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@ -1044,15 +1040,15 @@ toast_fetch_datum(varattrib *attr)
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chunksize, residx,
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attr->va_content.va_external.va_valueid);
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}
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else
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else if (residx < numchunks)
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{
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if ((residx * TOAST_MAX_CHUNK_SIZE + chunksize) != ressize)
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elog(ERROR, "unexpected chunk size %d in chunk %d for toast value %u",
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chunksize, residx,
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attr->va_content.va_external.va_valueid);
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}
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if (chunks_found[residx]++ > 0)
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elog(ERROR, "chunk %d for toast value %u appears multiple times",
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else
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elog(ERROR, "unexpected chunk number %d for toast value %u",
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residx,
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attr->va_content.va_external.va_valueid);
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@ -1064,16 +1060,16 @@ toast_fetch_datum(varattrib *attr)
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chunksize);
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ReleaseBuffer(buffer);
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nextidx++;
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}
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/*
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* Final checks that we successfully fetched the datum
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*/
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if (memcmp(chunks_found, chunks_expected, numchunks) != 0)
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elog(ERROR, "not all toast chunks found for value %u",
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if (nextidx != numchunks)
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elog(ERROR, "missing chunk number %d for toast value %u",
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nextidx,
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attr->va_content.va_external.va_valueid);
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pfree(chunks_expected);
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pfree(chunks_found);
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/*
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* End scan and close relations
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@ -1,14 +1,22 @@
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/*-------------------------------------------------------------------------
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*
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* tqual.c
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* POSTGRES "time" qualification code.
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* POSTGRES "time" qualification code, ie, tuple visibility rules.
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*
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* NOTE: all the HeapTupleSatisfies routines will update the tuple's
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* "hint" status bits if we see that the inserting or deleting transaction
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* has now committed or aborted. The caller is responsible for noticing any
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* change in t_infomask and scheduling a disk write if so. Note that the
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* caller must hold at least a shared buffer context lock on the buffer
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* containing the tuple. (VACUUM FULL assumes it's sufficient to have
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* exclusive lock on the containing relation, instead.)
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*
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*
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* Portions Copyright (c) 1996-2001, 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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* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.46 2002/01/11 20:07:03 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.47 2002/01/16 20:29:02 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -36,8 +44,7 @@ bool ReferentialIntegritySnapshotOverride = false;
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*
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* Note:
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* Assumes heap tuple is valid.
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*/
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/*
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*
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* The satisfaction of "itself" requires the following:
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*
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* ((Xmin == my-transaction && the row was updated by the current transaction, and
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@ -153,8 +160,7 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple)
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*
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* Note:
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* Assumes heap tuple is valid.
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*/
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/*
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*
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* The satisfaction of "now" requires the following:
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*
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* ((Xmin == my-transaction && changed by the current transaction
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@ -288,6 +294,71 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple)
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return false;
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}
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/*
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* HeapTupleSatisfiesToast
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* True iff heap tuple is valid for TOAST usage.
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*
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* This is a simplified version that only checks for VACUUM moving conditions.
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* It's appropriate for TOAST usage because TOAST really doesn't want to do
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* its own time qual checks; if you can see the main-table row that contains
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* a TOAST reference, you should be able to see the TOASTed value. However,
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* vacuuming a TOAST table is independent of the main table, and in case such
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* a vacuum fails partway through, we'd better do this much checking.
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*
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* Among other things, this means you can't do UPDATEs of rows in a TOAST
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* table.
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*/
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bool
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HeapTupleSatisfiesToast(HeapTupleHeader tuple)
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{
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if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
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{
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if (tuple->t_infomask & HEAP_XMIN_INVALID)
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return false;
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if (tuple->t_infomask & HEAP_MOVED_OFF)
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{
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if (TransactionIdIsCurrentTransactionId((TransactionId) tuple->t_cmin))
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return false;
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if (!TransactionIdIsInProgress((TransactionId) tuple->t_cmin))
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{
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if (TransactionIdDidCommit((TransactionId) tuple->t_cmin))
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{
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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return false;
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}
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tuple->t_infomask |= HEAP_XMIN_COMMITTED;
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}
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}
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else if (tuple->t_infomask & HEAP_MOVED_IN)
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{
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if (!TransactionIdIsCurrentTransactionId((TransactionId) tuple->t_cmin))
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{
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if (TransactionIdIsInProgress((TransactionId) tuple->t_cmin))
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return false;
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if (TransactionIdDidCommit((TransactionId) tuple->t_cmin))
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tuple->t_infomask |= HEAP_XMIN_COMMITTED;
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else
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{
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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return false;
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}
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}
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}
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}
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/* otherwise assume the tuple is valid for TOAST. */
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return true;
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}
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/*
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* HeapTupleSatisfiesUpdate
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* Check whether a tuple can be updated.
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*
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* This applies exactly the same checks as HeapTupleSatisfiesNow,
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* but returns a more-detailed result code, since UPDATE needs to know
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* more than "is it visible?"
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*/
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int
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HeapTupleSatisfiesUpdate(HeapTuple htuple)
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{
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@ -404,6 +475,18 @@ HeapTupleSatisfiesUpdate(HeapTuple htuple)
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return HeapTupleUpdated; /* updated by other */
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}
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/*
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* HeapTupleSatisfiesDirty
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* True iff heap tuple is valid, including effects of concurrent xacts.
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*
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* This is essentially like HeapTupleSatisfiesItself as far as effects of
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* the current transaction and committed/aborted xacts are concerned.
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* However, we also include the effects of other xacts still in progress.
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*
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* Returns extra information in the global variable SnapshotDirty, namely
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* xids of concurrent xacts that affected the tuple. Also, the tuple's
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* t_ctid (forward link) is returned if it's being updated.
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*/
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bool
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HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
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{
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@ -516,6 +599,18 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
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return false; /* updated by other */
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}
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/*
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* HeapTupleSatisfiesSnapshot
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* True iff heap tuple is valid for the given snapshot.
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*
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* This is the same as HeapTupleSatisfiesNow, except that transactions that
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* were in progress or as yet unstarted when the snapshot was taken will
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* be treated as uncommitted, even if they really have committed by now.
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*
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* (Notice, however, that the tuple status hint bits will be updated on the
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* basis of the true state of the transaction, even if we then pretend we
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* can't see it.)
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*/
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bool
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HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
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{
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@ -658,11 +753,6 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
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* deleted by XIDs >= OldestXmin are deemed "recently dead"; they might
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* still be visible to some open transaction, so we can't remove them,
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* even if we see that the deleting transaction has committed.
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*
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* As with the other HeapTupleSatisfies routines, we may update the tuple's
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* "hint" status bits if we see that the inserting or deleting transaction
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* has now committed or aborted. The caller is responsible for noticing any
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* change in t_infomask and scheduling a disk write if so.
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*/
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HTSV_Result
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HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
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@ -808,13 +898,21 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
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}
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/*
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* SetQuerySnapshot
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* Initialize query snapshot for a new query
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*
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* The SerializableSnapshot is the first one taken in a transaction.
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* In serializable mode we just use that one throughout the transaction.
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* In read-committed mode, we take a new snapshot at the start of each query.
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*/
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void
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SetQuerySnapshot(void)
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{
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/* Initialize snapshot overriding to false */
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ReferentialIntegritySnapshotOverride = false;
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/* 1st call in xaction */
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/* 1st call in xaction? */
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if (SerializableSnapshot == NULL)
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{
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SerializableSnapshot = GetSnapshotData(true);
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@ -837,6 +935,10 @@ SetQuerySnapshot(void)
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Assert(QuerySnapshot != NULL);
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}
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/*
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* FreeXactSnapshot
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* Free snapshot(s) at end of transaction.
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*/
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void
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FreeXactSnapshot(void)
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{
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@ -1,14 +1,14 @@
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/*-------------------------------------------------------------------------
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*
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* tqual.h
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* POSTGRES "time" qualification definitions.
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* POSTGRES "time" qualification definitions, ie, tuple visibility rules.
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*
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* Should be moved/renamed... - vadim 07/28/98
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*
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* Portions Copyright (c) 1996-2001, 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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* $Id: tqual.h,v 1.37 2001/11/05 17:46:36 momjian Exp $
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* $Id: tqual.h,v 1.38 2002/01/16 20:29:02 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -34,6 +34,7 @@ typedef SnapshotData *Snapshot;
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#define SnapshotNow ((Snapshot) 0x0)
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#define SnapshotSelf ((Snapshot) 0x1)
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#define SnapshotAny ((Snapshot) 0x2)
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#define SnapshotToast ((Snapshot) 0x3)
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extern DLLIMPORT Snapshot SnapshotDirty;
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extern DLLIMPORT Snapshot QuerySnapshot;
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@ -44,37 +45,36 @@ extern bool ReferentialIntegritySnapshotOverride;
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#define IsSnapshotNow(snapshot) ((Snapshot) (snapshot) == SnapshotNow)
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#define IsSnapshotSelf(snapshot) ((Snapshot) (snapshot) == SnapshotSelf)
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#define IsSnapshotAny(snapshot) ((Snapshot) (snapshot) == SnapshotAny)
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#define IsSnapshotToast(snapshot) ((Snapshot) (snapshot) == SnapshotToast)
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#define IsSnapshotDirty(snapshot) ((Snapshot) (snapshot) == SnapshotDirty)
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/*
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* HeapTupleSatisfiesVisibility
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* True iff heap tuple satsifies a time qual.
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* True iff heap tuple satisfies a time qual.
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*
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* Notes:
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* Assumes heap tuple is valid.
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* Beware of multiple evaluations of arguments.
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* Beware of multiple evaluations of snapshot argument.
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*/
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#define HeapTupleSatisfiesVisibility(tuple, snapshot) \
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( \
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TransactionIdEquals((tuple)->t_data->t_xmax, BootstrapTransactionId) ? \
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false \
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(IsSnapshotNow(snapshot) ? \
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HeapTupleSatisfiesNow((tuple)->t_data) \
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: \
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(IsSnapshotSelf(snapshot) ? \
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HeapTupleSatisfiesItself((tuple)->t_data) \
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: \
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( \
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IsSnapshotAny(snapshot) ? \
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(IsSnapshotAny(snapshot) ? \
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true \
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: \
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(IsSnapshotSelf(snapshot) ? \
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HeapTupleSatisfiesItself((tuple)->t_data) \
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(IsSnapshotToast(snapshot) ? \
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HeapTupleSatisfiesToast((tuple)->t_data) \
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: \
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(IsSnapshotNow(snapshot) ? \
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HeapTupleSatisfiesNow((tuple)->t_data) \
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(IsSnapshotDirty(snapshot) ? \
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HeapTupleSatisfiesDirty((tuple)->t_data) \
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: \
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(IsSnapshotDirty(snapshot) ? \
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HeapTupleSatisfiesDirty((tuple)->t_data) \
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: \
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HeapTupleSatisfiesSnapshot((tuple)->t_data, snapshot) \
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) \
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HeapTupleSatisfiesSnapshot((tuple)->t_data, snapshot) \
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) \
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) \
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) \
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) \
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@ -93,14 +93,15 @@ typedef enum
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HEAPTUPLE_DEAD, /* tuple is dead and deletable */
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HEAPTUPLE_LIVE, /* tuple is live (committed, no deleter) */
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HEAPTUPLE_RECENTLY_DEAD, /* tuple is dead, but not deletable yet */
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HEAPTUPLE_INSERT_IN_PROGRESS, /* inserting xact is still in
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* progress */
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HEAPTUPLE_INSERT_IN_PROGRESS, /* inserting xact is still in
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* progress */
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HEAPTUPLE_DELETE_IN_PROGRESS /* deleting xact is still in progress */
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} HTSV_Result;
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extern bool HeapTupleSatisfiesItself(HeapTupleHeader tuple);
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extern bool HeapTupleSatisfiesNow(HeapTupleHeader tuple);
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extern bool HeapTupleSatisfiesDirty(HeapTupleHeader tuple);
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extern bool HeapTupleSatisfiesToast(HeapTupleHeader tuple);
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extern bool HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple,
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Snapshot snapshot);
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extern int HeapTupleSatisfiesUpdate(HeapTuple tuple);
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