2017-02-02 20:12:58 +01:00
CREATE TABLE test_hash (a int, b text);
INSERT INTO test_hash VALUES (1, 'one');
CREATE INDEX test_hash_a_idx ON test_hash USING hash (a);
\x
SELECT hash_page_type(get_raw_page('test_hash_a_idx', 0));
-[ RECORD 1 ]--+---------
hash_page_type | metapage
SELECT hash_page_type(get_raw_page('test_hash_a_idx', 1));
-[ RECORD 1 ]--+-------
hash_page_type | bucket
SELECT hash_page_type(get_raw_page('test_hash_a_idx', 2));
-[ RECORD 1 ]--+-------
hash_page_type | bucket
SELECT hash_page_type(get_raw_page('test_hash_a_idx', 3));
-[ RECORD 1 ]--+-------
hash_page_type | bucket
SELECT hash_page_type(get_raw_page('test_hash_a_idx', 4));
-[ RECORD 1 ]--+-------
hash_page_type | bucket
SELECT hash_page_type(get_raw_page('test_hash_a_idx', 5));
-[ RECORD 1 ]--+-------
hash_page_type | bitmap
SELECT hash_page_type(get_raw_page('test_hash_a_idx', 6));
ERROR: block number 6 is out of range for relation "test_hash_a_idx"
SELECT * FROM hash_bitmap_info('test_hash_a_idx', 0);
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ERROR: invalid overflow block number 0
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SELECT * FROM hash_bitmap_info('test_hash_a_idx', 1);
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ERROR: invalid overflow block number 1
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SELECT * FROM hash_bitmap_info('test_hash_a_idx', 2);
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ERROR: invalid overflow block number 2
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SELECT * FROM hash_bitmap_info('test_hash_a_idx', 3);
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ERROR: invalid overflow block number 3
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SELECT * FROM hash_bitmap_info('test_hash_a_idx', 4);
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ERROR: invalid overflow block number 4
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SELECT * FROM hash_bitmap_info('test_hash_a_idx', 5);
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ERROR: invalid overflow block number 5
2017-02-03 17:06:41 +01:00
SELECT magic, version, ntuples, bsize, bmsize, bmshift, maxbucket, highmask,
lowmask, ovflpoint, firstfree, nmaps, procid, spares, mapp FROM
hash_metapage_info(get_raw_page('test_hash_a_idx', 0));
2017-02-02 20:12:58 +01:00
-[ RECORD 1 ]----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
magic | 105121344
version | 2
ntuples | 1
bsize | 8152
bmsize | 4096
bmshift | 15
maxbucket | 3
highmask | 7
lowmask | 3
ovflpoint | 2
firstfree | 0
nmaps | 1
procid | 450
spares | {0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
mapp | {5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
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SELECT magic, version, ntuples, bsize, bmsize, bmshift, maxbucket, highmask,
lowmask, ovflpoint, firstfree, nmaps, procid, spares, mapp FROM
hash_metapage_info(get_raw_page('test_hash_a_idx', 1));
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ERROR: page is not a hash meta page
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SELECT magic, version, ntuples, bsize, bmsize, bmshift, maxbucket, highmask,
lowmask, ovflpoint, firstfree, nmaps, procid, spares, mapp FROM
hash_metapage_info(get_raw_page('test_hash_a_idx', 2));
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ERROR: page is not a hash meta page
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SELECT magic, version, ntuples, bsize, bmsize, bmshift, maxbucket, highmask,
lowmask, ovflpoint, firstfree, nmaps, procid, spares, mapp FROM
hash_metapage_info(get_raw_page('test_hash_a_idx', 3));
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ERROR: page is not a hash meta page
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SELECT magic, version, ntuples, bsize, bmsize, bmshift, maxbucket, highmask,
lowmask, ovflpoint, firstfree, nmaps, procid, spares, mapp FROM
hash_metapage_info(get_raw_page('test_hash_a_idx', 4));
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ERROR: page is not a hash meta page
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SELECT magic, version, ntuples, bsize, bmsize, bmshift, maxbucket, highmask,
lowmask, ovflpoint, firstfree, nmaps, procid, spares, mapp FROM
hash_metapage_info(get_raw_page('test_hash_a_idx', 5));
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ERROR: page is not a hash meta page
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SELECT live_items, dead_items, page_size, hasho_prevblkno, hasho_nextblkno,
hasho_bucket, hasho_flag, hasho_page_id FROM
hash_page_stats(get_raw_page('test_hash_a_idx', 0));
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ERROR: page is not a hash bucket or overflow page
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SELECT live_items, dead_items, page_size, hasho_prevblkno, hasho_nextblkno,
hasho_bucket, hasho_flag, hasho_page_id FROM
hash_page_stats(get_raw_page('test_hash_a_idx', 1));
2017-02-02 20:12:58 +01:00
-[ RECORD 1 ]---+-----------
live_items | 0
dead_items | 0
page_size | 8192
Cache hash index's metapage in rel->rd_amcache.
This avoids a very significant amount of buffer manager traffic and
contention when scanning hash indexes, because it's no longer
necessary to lock and pin the metapage for every scan. We do need
some way of figuring out when the cache is too stale to use any more,
so that when we lock the primary bucket page to which the cached
metapage points us, we can tell whether a split has occurred since we
cached the metapage data. To do that, we use the hash_prevblkno field
in the primary bucket page, which would otherwise always be set to
InvalidBuffer.
This patch contains code so that it will continue working (although
less efficiently) with hash indexes built before this change, but
perhaps we should consider bumping the hash version and ripping out
the compatibility code. That decision can be made later, though.
Mithun Cy, reviewed by Jesper Pedersen, Amit Kapila, and by me.
Before committing, I made a number of cosmetic changes to the last
posted version of the patch, adjusted _hash_getcachedmetap to be more
careful about order of operation, and made some necessary updates to
the pageinspect documentation and regression tests.
2017-02-07 18:24:25 +01:00
hasho_prevblkno | 3
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hasho_nextblkno | 4294967295
hasho_bucket | 0
hasho_flag | 2
hasho_page_id | 65408
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SELECT live_items, dead_items, page_size, hasho_prevblkno, hasho_nextblkno,
hasho_bucket, hasho_flag, hasho_page_id FROM
hash_page_stats(get_raw_page('test_hash_a_idx', 2));
2017-02-02 20:12:58 +01:00
-[ RECORD 1 ]---+-----------
live_items | 0
dead_items | 0
page_size | 8192
Cache hash index's metapage in rel->rd_amcache.
This avoids a very significant amount of buffer manager traffic and
contention when scanning hash indexes, because it's no longer
necessary to lock and pin the metapage for every scan. We do need
some way of figuring out when the cache is too stale to use any more,
so that when we lock the primary bucket page to which the cached
metapage points us, we can tell whether a split has occurred since we
cached the metapage data. To do that, we use the hash_prevblkno field
in the primary bucket page, which would otherwise always be set to
InvalidBuffer.
This patch contains code so that it will continue working (although
less efficiently) with hash indexes built before this change, but
perhaps we should consider bumping the hash version and ripping out
the compatibility code. That decision can be made later, though.
Mithun Cy, reviewed by Jesper Pedersen, Amit Kapila, and by me.
Before committing, I made a number of cosmetic changes to the last
posted version of the patch, adjusted _hash_getcachedmetap to be more
careful about order of operation, and made some necessary updates to
the pageinspect documentation and regression tests.
2017-02-07 18:24:25 +01:00
hasho_prevblkno | 3
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hasho_nextblkno | 4294967295
hasho_bucket | 1
hasho_flag | 2
hasho_page_id | 65408
2017-02-03 17:06:41 +01:00
SELECT live_items, dead_items, page_size, hasho_prevblkno, hasho_nextblkno,
hasho_bucket, hasho_flag, hasho_page_id FROM
hash_page_stats(get_raw_page('test_hash_a_idx', 3));
2017-02-02 20:12:58 +01:00
-[ RECORD 1 ]---+-----------
live_items | 1
dead_items | 0
page_size | 8192
Cache hash index's metapage in rel->rd_amcache.
This avoids a very significant amount of buffer manager traffic and
contention when scanning hash indexes, because it's no longer
necessary to lock and pin the metapage for every scan. We do need
some way of figuring out when the cache is too stale to use any more,
so that when we lock the primary bucket page to which the cached
metapage points us, we can tell whether a split has occurred since we
cached the metapage data. To do that, we use the hash_prevblkno field
in the primary bucket page, which would otherwise always be set to
InvalidBuffer.
This patch contains code so that it will continue working (although
less efficiently) with hash indexes built before this change, but
perhaps we should consider bumping the hash version and ripping out
the compatibility code. That decision can be made later, though.
Mithun Cy, reviewed by Jesper Pedersen, Amit Kapila, and by me.
Before committing, I made a number of cosmetic changes to the last
posted version of the patch, adjusted _hash_getcachedmetap to be more
careful about order of operation, and made some necessary updates to
the pageinspect documentation and regression tests.
2017-02-07 18:24:25 +01:00
hasho_prevblkno | 3
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hasho_nextblkno | 4294967295
hasho_bucket | 2
hasho_flag | 2
hasho_page_id | 65408
2017-02-03 17:06:41 +01:00
SELECT live_items, dead_items, page_size, hasho_prevblkno, hasho_nextblkno,
hasho_bucket, hasho_flag, hasho_page_id FROM
hash_page_stats(get_raw_page('test_hash_a_idx', 4));
2017-02-02 20:12:58 +01:00
-[ RECORD 1 ]---+-----------
live_items | 0
dead_items | 0
page_size | 8192
Cache hash index's metapage in rel->rd_amcache.
This avoids a very significant amount of buffer manager traffic and
contention when scanning hash indexes, because it's no longer
necessary to lock and pin the metapage for every scan. We do need
some way of figuring out when the cache is too stale to use any more,
so that when we lock the primary bucket page to which the cached
metapage points us, we can tell whether a split has occurred since we
cached the metapage data. To do that, we use the hash_prevblkno field
in the primary bucket page, which would otherwise always be set to
InvalidBuffer.
This patch contains code so that it will continue working (although
less efficiently) with hash indexes built before this change, but
perhaps we should consider bumping the hash version and ripping out
the compatibility code. That decision can be made later, though.
Mithun Cy, reviewed by Jesper Pedersen, Amit Kapila, and by me.
Before committing, I made a number of cosmetic changes to the last
posted version of the patch, adjusted _hash_getcachedmetap to be more
careful about order of operation, and made some necessary updates to
the pageinspect documentation and regression tests.
2017-02-07 18:24:25 +01:00
hasho_prevblkno | 3
2017-02-02 20:12:58 +01:00
hasho_nextblkno | 4294967295
hasho_bucket | 3
hasho_flag | 2
hasho_page_id | 65408
2017-02-03 17:06:41 +01:00
SELECT live_items, dead_items, page_size, hasho_prevblkno, hasho_nextblkno,
hasho_bucket, hasho_flag, hasho_page_id FROM
hash_page_stats(get_raw_page('test_hash_a_idx', 5));
2017-02-02 20:12:58 +01:00
ERROR: page is not a hash bucket or overflow page
SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 0));
ERROR: page is not a hash bucket or overflow page
SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 1));
(0 rows)
SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 2));
(0 rows)
SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 3));
-[ RECORD 1 ]----------
itemoffset | 1
ctid | (0,1)
data | 2389907270
SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 4));
(0 rows)
SELECT * FROM hash_page_items(get_raw_page('test_hash_a_idx', 5));
ERROR: page is not a hash bucket or overflow page
DROP TABLE test_hash;