On 21.08.2020 19:43, Ibrar Ahmed wrote:
On Wed, Aug 19, 2020 at 6:15 PM Anastasia Lubennikova
<a.lubennik...@postgrespro.ru <mailto:a.lubennik...@postgrespro.ru>>
wrote:
On 18.08.2020 02:54, Alvaro Herrera wrote:
> On 2020-Aug-14, Ibrar Ahmed wrote:
>
>> The table used for the test contains three columns (integer, text,
>> varchar).
>> The total number of rows is 10000000 in total.
>>
>> Unpatched (Master: 92c12e46d5f1e25fc85608a6d6a19b8f5ea02600)
>> COPY: 9069.432 ms vacuum; 2567.961ms
>> COPY: 9004.533 ms vacuum: 2553.075ms
>> COPY: 8832.422 ms vacuum: 2540.742ms
>>
>> Patched (Master: 92c12e46d5f1e25fc85608a6d6a19b8f5ea02600)
>> COPY: 10031.723 ms vacuum: 127.524 ms
>> COPY: 9985.109 ms vacuum: 39.953 ms
>> COPY: 9283.373 ms vacuum: 37.137 ms
>>
>> Time to take the copy slightly increased but the vacuum time
significantly
>> decrease.
> "Slightly"? It seems quite a large performance drop to me --
more than
> 10%. Where is that time being spent? Andres said in [1] that he
> thought the performance shouldn't be affected noticeably, but this
> doesn't seem to hold true. As I understand, the idea was that there
> would be little or no additional WAL records .. only flags in the
> existing record. So what is happening?
>
> [1]
https://postgr.es/m/20190408010427.4l63qr7h2fjcy...@alap3.anarazel.de
I agree that 10% performance drop is not what we expect with this
patch.
Ibrar, can you share more info about your tests? I'd like to
reproduce
this slowdown and fix it, if necessary.
Here is my test;
postgres=# BEGIN;
BEGIN
postgres=*# TRUNCATE foo;
TRUNCATE TABLE
postgres=*# COPY foo(id, name, address) FROM '/home/ibrar/bar.csv'
DELIMITER ',' FREEZE;
COPY 10000000
--
Ibrar Ahmed
I've repeated the test and didn't notice any slowdown for COPY FREEZE.
Test data is here [1].
The numbers do fluctuate a bit, but there is no dramatic difference
between master and patched version. So I assume that the performance
drop in your test has something to do with the measurement error.
Unless, you have some non-default configuration that could affect it.
patched:
COPY: 12327,090 ms vacuum: 37,555 ms
COPY: 12939,540 ms vacuum: 35,703 ms
COPY: 12245,819 ms vacuum: 36,273 ms
master:
COPY
COPY: 13253,605 ms vacuum: 3592,849 ms
COPY: 12619,428 ms vacuum: 4253,836 ms
COPY: 12512,940 ms vacuum: 4009,847 ms
I also slightly cleaned up comments, so the new version of the patch is
attached. As this is just a performance optimization documentation is
not needed. It would be great, if other reviewers could run some
independent performance tests, as I believe that this patch is ready for
committer.
[1] https://drive.google.com/file/d/11r19NX6yyPjvxdDub8Ce-kmApRurp4Nx/view
--
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Companyt
diff --git a/contrib/pg_visibility/expected/pg_visibility.out b/contrib/pg_visibility/expected/pg_visibility.out
index ca4b6e186b..0017e3415c 100644
--- a/contrib/pg_visibility/expected/pg_visibility.out
+++ b/contrib/pg_visibility/expected/pg_visibility.out
@@ -179,6 +179,69 @@ select pg_truncate_visibility_map('test_partition');
(1 row)
+-- test copy freeze
+create table copyfreeze (a int, b char(1500));
+-- load all rows via COPY FREEZE and ensure that all pages are set all-visible
+-- and all-frozen.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+commit;
+select * from pg_visibility_map('copyfreeze');
+ blkno | all_visible | all_frozen
+-------+-------------+------------
+ 0 | t | t
+ 1 | t | t
+ 2 | t | t
+(3 rows)
+
+select * from pg_check_frozen('copyfreeze');
+ t_ctid
+--------
+(0 rows)
+
+-- load half the rows via regular COPY and rest via COPY FREEZE. The pages
+-- which are touched by regular COPY must not be set all-visible/all-frozen. On
+-- the other hand, pages allocated by COPY FREEZE should be marked
+-- all-frozen/all-visible.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin;
+copy copyfreeze from stdin freeze;
+commit;
+select * from pg_visibility_map('copyfreeze');
+ blkno | all_visible | all_frozen
+-------+-------------+------------
+ 0 | f | f
+ 1 | f | f
+ 2 | t | t
+(3 rows)
+
+select * from pg_check_frozen('copyfreeze');
+ t_ctid
+--------
+(0 rows)
+
+-- Try a mix of regular COPY and COPY FREEZE.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+copy copyfreeze from stdin;
+copy copyfreeze from stdin freeze;
+commit;
+select * from pg_visibility_map('copyfreeze');
+ blkno | all_visible | all_frozen
+-------+-------------+------------
+ 0 | t | t
+ 1 | f | f
+ 2 | t | t
+(3 rows)
+
+select * from pg_check_frozen('copyfreeze');
+ t_ctid
+--------
+(0 rows)
+
-- cleanup
drop table test_partitioned;
drop view test_view;
@@ -188,3 +251,4 @@ drop server dummy_server;
drop foreign data wrapper dummy;
drop materialized view matview_visibility_test;
drop table regular_table;
+drop table copyfreeze;
diff --git a/contrib/pg_visibility/sql/pg_visibility.sql b/contrib/pg_visibility/sql/pg_visibility.sql
index f79b54480b..ec1afd4906 100644
--- a/contrib/pg_visibility/sql/pg_visibility.sql
+++ b/contrib/pg_visibility/sql/pg_visibility.sql
@@ -94,6 +94,82 @@ select count(*) > 0 from pg_visibility_map_summary('test_partition');
select * from pg_check_frozen('test_partition'); -- hopefully none
select pg_truncate_visibility_map('test_partition');
+-- test copy freeze
+create table copyfreeze (a int, b char(1500));
+
+-- load all rows via COPY FREEZE and ensure that all pages are set all-visible
+-- and all-frozen.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+1 '1'
+2 '2'
+3 '3'
+4 '4'
+5 '5'
+6 '6'
+7 '7'
+8 '8'
+9 '9'
+10 '10'
+11 '11'
+12 '12'
+\.
+commit;
+select * from pg_visibility_map('copyfreeze');
+select * from pg_check_frozen('copyfreeze');
+
+-- load half the rows via regular COPY and rest via COPY FREEZE. The pages
+-- which are touched by regular COPY must not be set all-visible/all-frozen. On
+-- the other hand, pages allocated by COPY FREEZE should be marked
+-- all-frozen/all-visible.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin;
+1 '1'
+2 '2'
+3 '3'
+4 '4'
+5 '5'
+6 '6'
+\.
+copy copyfreeze from stdin freeze;
+7 '7'
+8 '8'
+9 '9'
+10 '10'
+11 '11'
+12 '12'
+\.
+commit;
+select * from pg_visibility_map('copyfreeze');
+select * from pg_check_frozen('copyfreeze');
+
+-- Try a mix of regular COPY and COPY FREEZE.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+1 '1'
+2 '2'
+3 '3'
+4 '4'
+5 '5'
+\.
+copy copyfreeze from stdin;
+6 '6'
+\.
+copy copyfreeze from stdin freeze;
+7 '7'
+8 '8'
+9 '9'
+10 '10'
+11 '11'
+12 '12'
+\.
+commit;
+select * from pg_visibility_map('copyfreeze');
+select * from pg_check_frozen('copyfreeze');
+
-- cleanup
drop table test_partitioned;
drop view test_view;
@@ -103,3 +179,4 @@ drop server dummy_server;
drop foreign data wrapper dummy;
drop materialized view matview_visibility_test;
drop table regular_table;
+drop table copyfreeze;
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 9b5f417eac..338854d4ae 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -2105,6 +2105,7 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
int ndone;
PGAlignedBlock scratch;
Page page;
+ Buffer vmbuffer = InvalidBuffer;
bool needwal;
Size saveFreeSpace;
bool need_tuple_data = RelationIsLogicallyLogged(relation);
@@ -2159,8 +2160,9 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
while (ndone < ntuples)
{
Buffer buffer;
- Buffer vmbuffer = InvalidBuffer;
+ bool starting_with_empty_page;
bool all_visible_cleared = false;
+ bool all_frozen_set = false;
int nthispage;
CHECK_FOR_INTERRUPTS();
@@ -2168,12 +2170,20 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
/*
* Find buffer where at least the next tuple will fit. If the page is
* all-visible, this will also pin the requisite visibility map page.
+ *
+ * Also pin visibility map page if COPY FREEZE inserts tuples into an
+ * empty page. See all_frozen_set below.
*/
buffer = RelationGetBufferForTuple(relation, heaptuples[ndone]->t_len,
InvalidBuffer, options, bistate,
&vmbuffer, NULL);
page = BufferGetPage(buffer);
+ starting_with_empty_page = PageGetMaxOffsetNumber(page) == 0;
+
+ if (starting_with_empty_page && (options & HEAP_INSERT_FROZEN))
+ all_frozen_set = true;
+
/* NO EREPORT(ERROR) from here till changes are logged */
START_CRIT_SECTION();
@@ -2207,7 +2217,11 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
log_heap_new_cid(relation, heaptup);
}
- if (PageIsAllVisible(page))
+ /*
+ * If the page is all visible, need to clear that, unless we're only
+ * going to add further frozen rows to it.
+ */
+ if (PageIsAllVisible(page) && !(options & HEAP_INSERT_FROZEN))
{
all_visible_cleared = true;
PageClearAllVisible(page);
@@ -2215,6 +2229,12 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
BufferGetBlockNumber(buffer),
vmbuffer, VISIBILITYMAP_VALID_BITS);
}
+ /*
+ * If we're only adding already frozen rows, and the page was
+ * previously empty, mark it as all-visible.
+ */
+ else if (all_frozen_set)
+ PageSetAllVisible(page);
/*
* XXX Should we set PageSetPrunable on this page ? See heap_insert()
@@ -2238,8 +2258,7 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
* If the page was previously empty, we can reinit the page
* instead of restoring the whole thing.
*/
- init = (ItemPointerGetOffsetNumber(&(heaptuples[ndone]->t_self)) == FirstOffsetNumber &&
- PageGetMaxOffsetNumber(page) == FirstOffsetNumber + nthispage - 1);
+ init = starting_with_empty_page;
/* allocate xl_heap_multi_insert struct from the scratch area */
xlrec = (xl_heap_multi_insert *) scratchptr;
@@ -2257,7 +2276,13 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
/* the rest of the scratch space is used for tuple data */
tupledata = scratchptr;
- xlrec->flags = all_visible_cleared ? XLH_INSERT_ALL_VISIBLE_CLEARED : 0;
+ xlrec->flags = 0;
+ Assert (!(all_visible_cleared && all_frozen_set));
+ if (all_visible_cleared)
+ xlrec->flags |= XLH_INSERT_ALL_VISIBLE_CLEARED;
+ if (all_frozen_set)
+ xlrec->flags |= XLH_INSERT_ALL_FROZEN_SET;
+
xlrec->ntuples = nthispage;
/*
@@ -2331,13 +2356,39 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
END_CRIT_SECTION();
- UnlockReleaseBuffer(buffer);
- if (vmbuffer != InvalidBuffer)
- ReleaseBuffer(vmbuffer);
+ if (all_frozen_set)
+ {
+ Assert(PageIsAllVisible(page));
+ /*
+ * vmbuffer should be already pinned by RelationGetBufferForTuple,
+ * Though, it's fine if is not. all_frozen is just an optimization.
+ */
+ if (visibilitymap_pin_ok(BufferGetBlockNumber(buffer), vmbuffer))
+ /*
+ * It's fine to use InvalidTransactionId here - this is only used
+ * when HEAP_INSERT_FROZEN is specified, which intentionally
+ * violates visibility rules.
+ */
+ visibilitymap_set(relation, BufferGetBlockNumber(buffer), buffer,
+ InvalidXLogRecPtr, vmbuffer,
+ InvalidTransactionId,
+ VISIBILITYMAP_ALL_VISIBLE | VISIBILITYMAP_ALL_FROZEN);
+ }
+
+ UnlockReleaseBuffer(buffer);
ndone += nthispage;
+
+ /*
+ * NB: Only release vmbuffer after inserting all tuples - it's fairly
+ * likely that we'll insert into subsequent heap pages that are likely
+ * to use the same vm page.
+ */
}
+ if (vmbuffer != InvalidBuffer)
+ ReleaseBuffer(vmbuffer);
+
/*
* We're done with the actual inserts. Check for conflicts again, to
* ensure that all rw-conflicts in to these inserts are detected. Without
@@ -8246,7 +8297,8 @@ heap_xlog_multi_insert(XLogReaderState *record)
* The visibility map may need to be fixed even if the heap page is
* already up-to-date.
*/
- if (xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED)
+ if ((xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED) &&
+ !(xlrec->flags & XLH_INSERT_ALL_FROZEN_SET))
{
Relation reln = CreateFakeRelcacheEntry(rnode);
Buffer vmbuffer = InvalidBuffer;
@@ -8330,6 +8382,8 @@ heap_xlog_multi_insert(XLogReaderState *record)
if (xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED)
PageClearAllVisible(page);
+ if (xlrec->flags & XLH_INSERT_ALL_FROZEN_SET)
+ PageSetAllVisible(page);
MarkBufferDirty(buffer);
}
diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c
index aa3f14c019..b264ff53d7 100644
--- a/src/backend/access/heap/hio.c
+++ b/src/backend/access/heap/hio.c
@@ -422,6 +422,14 @@ loop:
buffer = ReadBufferBI(relation, targetBlock, RBM_NORMAL, bistate);
if (PageIsAllVisible(BufferGetPage(buffer)))
visibilitymap_pin(relation, targetBlock, vmbuffer);
+ /*
+ * This is for COPY FREEZE needs. If page is empty,
+ * pin vmbuffer to set all_frozen bit
+ */
+ if ((options & HEAP_INSERT_FROZEN) &&
+ (PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0))
+ visibilitymap_pin(relation, BufferGetBlockNumber(buffer), vmbuffer);
+
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
}
else if (otherBlock == targetBlock)
@@ -608,6 +616,16 @@ loop:
PageInit(page, BufferGetPageSize(buffer), 0);
MarkBufferDirty(buffer);
+ /*
+ * This is for COPY FREEZE needs. If page is empty,
+ * pin vmbuffer to set all_frozen bit
+ */
+ if ((options & HEAP_INSERT_FROZEN))
+ {
+ Assert(PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0);
+ visibilitymap_pin(relation, BufferGetBlockNumber(buffer), vmbuffer);
+ }
+
/*
* Release the file-extension lock; it's now OK for someone else to extend
* the relation some more.
diff --git a/src/include/access/heapam_xlog.h b/src/include/access/heapam_xlog.h
index aa17f7df84..16c1fd5673 100644
--- a/src/include/access/heapam_xlog.h
+++ b/src/include/access/heapam_xlog.h
@@ -69,6 +69,9 @@
#define XLH_INSERT_CONTAINS_NEW_TUPLE (1<<3)
#define XLH_INSERT_ON_TOAST_RELATION (1<<4)
+/* all_frozen_set always implies all_visible_set */
+#define XLH_INSERT_ALL_FROZEN_SET (1<<5)
+
/*
* xl_heap_update flag values, 8 bits are available.
*/
