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Fix leaking of small spilled subtransactions during logical decoding.

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When, during logical decoding, a transaction gets too big, it's
contents get spilled to disk. Not just the top-transaction gets
spilled, but *also* all of its subtransactions, even if they're not
that large themselves.  Unfortunately we didn't clean up
such small spilled subtransactions from disk.

Fix that, by keeping better track of whether a transaction has been
spilled to disk.

Author: Andres Freund
Reported-By: Dmitriy Sarafannikov, Fabrízio de Royes Mello
Discussion:
    https://postgr.es/m/1457621358.355011041@f382.i.mail.ru
    https://postgr.es/m/CAFcNs+qNMhNYii4nxpO6gqsndiyxNDYV0S=JNq0v_sEE+9PHXg@mail.gmail.com
Backpatch: 9.4-, where logical decoding was introduced
This commit is contained in:
Andres Freund 2017-06-18 18:48:22 -07:00
parent b4166a8df9
commit 3bdea167eb
2 changed files with 13 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
src/backend/replication/logical/reorderbuffer.c
View File

@ -893,7 +893,7 @@ ReorderBufferIterTXNInit(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
ReorderBufferChange *cur_change;
if (txn->nentries != txn->nentries_mem)
if (txn->serialized)
{
/* serialize remaining changes */
ReorderBufferSerializeTXN(rb, txn);
@ -922,7 +922,7 @@ ReorderBufferIterTXNInit(ReorderBuffer *rb, ReorderBufferTXN *txn)
{
ReorderBufferChange *cur_change;
if (cur_txn->nentries != cur_txn->nentries_mem)
if (cur_txn->serialized)
{
/* serialize remaining changes */
ReorderBufferSerializeTXN(rb, cur_txn);
@ -1142,7 +1142,7 @@ ReorderBufferCleanupTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
Assert(found);
/* remove entries spilled to disk */
if (txn->nentries != txn->nentries_mem)
if (txn->serialized)
ReorderBufferRestoreCleanup(rb, txn);
/* deallocate */
@ -2124,6 +2124,7 @@ ReorderBufferSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
Assert(spilled == txn->nentries_mem);
Assert(dlist_is_empty(&txn->changes));
txn->nentries_mem = 0;
txn->serialized = true;
if (fd != -1)
CloseTransientFile(fd);

9
src/include/replication/reorderbuffer.h
View File

@ -212,6 +212,15 @@ typedef struct ReorderBufferTXN
*/
uint64 nentries_mem;
/*
* Has this transaction been spilled to disk? It's not always possible to
* deduce that fact by comparing nentries with nentries_mem, because
* e.g. subtransactions of a large transaction might get serialized
* together with the parent - if they're restored to memory they'd have
* nentries_mem == nentries.
*/
bool serialized;
/*
* List of ReorderBufferChange structs, including new Snapshots and new
* CommandIds