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Some words were duplicated while other places were grammatically incorrect, including one variable name in the code. Author: Otto Kekalainen, Justin Pryzby Discussion: https://postgr.es/m/7DDBEFC5-09B6-4325-B942-B563D1A24BDC@amazon.com
68 lines
2.8 KiB
Plaintext
68 lines
2.8 KiB
Plaintext
-- The gist_page_opaque_info() function prints the page's LSN. Normally,
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-- that's constant 1 (GistBuildLSN) on every page of a freshly built GiST
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-- index. But with wal_level=minimal, the whole relation is dumped to WAL at
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-- the end of the transaction if it's smaller than wal_skip_threshold, which
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-- updates the LSNs. Wrap the tests on gist_page_opaque_info() in the
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-- same transaction with the CREATE INDEX so that we see the LSNs before
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-- they are possibly overwritten at end of transaction.
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BEGIN;
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-- Create a test table and GiST index.
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CREATE TABLE test_gist AS SELECT point(i,i) p, i::text t FROM
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generate_series(1,1000) i;
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CREATE INDEX test_gist_idx ON test_gist USING gist (p);
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-- Page 0 is the root, the rest are leaf pages
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SELECT * FROM gist_page_opaque_info(get_raw_page('test_gist_idx', 0));
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lsn | nsn | rightlink | flags
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-----+-----+------------+-------
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0/1 | 0/0 | 4294967295 | {}
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(1 row)
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SELECT * FROM gist_page_opaque_info(get_raw_page('test_gist_idx', 1));
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lsn | nsn | rightlink | flags
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-----+-----+------------+--------
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0/1 | 0/0 | 4294967295 | {leaf}
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(1 row)
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SELECT * FROM gist_page_opaque_info(get_raw_page('test_gist_idx', 2));
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lsn | nsn | rightlink | flags
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-----+-----+-----------+--------
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0/1 | 0/0 | 1 | {leaf}
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(1 row)
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COMMIT;
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SELECT * FROM gist_page_items(get_raw_page('test_gist_idx', 0), 'test_gist_idx');
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itemoffset | ctid | itemlen | dead | keys
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------------+-----------+---------+------+-------------------
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1 | (1,65535) | 40 | f | (p)=((185,185))
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2 | (2,65535) | 40 | f | (p)=((370,370))
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3 | (3,65535) | 40 | f | (p)=((555,555))
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4 | (4,65535) | 40 | f | (p)=((740,740))
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5 | (5,65535) | 40 | f | (p)=((870,870))
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6 | (6,65535) | 40 | f | (p)=((1000,1000))
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(6 rows)
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SELECT * FROM gist_page_items(get_raw_page('test_gist_idx', 1), 'test_gist_idx') LIMIT 5;
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itemoffset | ctid | itemlen | dead | keys
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------------+-------+---------+------+-------------
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1 | (0,1) | 40 | f | (p)=((1,1))
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2 | (0,2) | 40 | f | (p)=((2,2))
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3 | (0,3) | 40 | f | (p)=((3,3))
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4 | (0,4) | 40 | f | (p)=((4,4))
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5 | (0,5) | 40 | f | (p)=((5,5))
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(5 rows)
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-- gist_page_items_bytea prints the raw key data as a bytea. The output of that is
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-- platform-dependent (endianness), so omit the actual key data from the output.
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SELECT itemoffset, ctid, itemlen FROM gist_page_items_bytea(get_raw_page('test_gist_idx', 0));
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itemoffset | ctid | itemlen
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------------+-----------+---------
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1 | (1,65535) | 40
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2 | (2,65535) | 40
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3 | (3,65535) | 40
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4 | (4,65535) | 40
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5 | (5,65535) | 40
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6 | (6,65535) | 40
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(6 rows)
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DROP TABLE test_gist;
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