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5c5629910f
* Add a test case for reading historic page versions Test read_page_at_lsn returns correct results when compared to page inspect. Validate possiblity of reading pages from dropped relation. Ensure funcitons read latest version when null lsn supplied. Check that functions do not poison buffer cache with stale page versions.
184 lines
7.4 KiB
Python
184 lines
7.4 KiB
Python
from contextlib import closing
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from fixtures.zenith_fixtures import ZenithEnv
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from fixtures.log_helper import log
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from psycopg2.errors import UndefinedTable
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from psycopg2.errors import IoError
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pytest_plugins = ("fixtures.zenith_fixtures")
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extensions = ["pageinspect", "zenith_test_utils", "pg_buffercache"]
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#
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# Validation of reading different page versions
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#
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def test_read_validation(zenith_simple_env: ZenithEnv):
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env = zenith_simple_env
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env.zenith_cli.create_branch("test_read_validation", "empty")
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pg = env.postgres.create_start("test_read_validation")
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log.info("postgres is running on 'test_read_validation' branch")
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with closing(pg.connect()) as con:
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with con.cursor() as c:
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for e in extensions:
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c.execute("create extension if not exists {};".format(e))
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c.execute("create table foo (c int) with (autovacuum_enabled = false)")
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c.execute("insert into foo values (1)")
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c.execute("select lsn, lower, upper from page_header(get_raw_page('foo', 'main', 0));")
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first = c.fetchone()
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c.execute("select relfilenode from pg_class where relname = 'foo'")
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relfilenode = c.fetchone()[0]
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c.execute("insert into foo values (2);")
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c.execute("select lsn, lower, upper from page_header(get_raw_page('foo', 'main', 0));")
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second = c.fetchone()
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assert first != second, "Failed to update page"
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log.info("Test table is populated, validating buffer cache")
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c.execute(
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"select count(*) from pg_buffercache where relfilenode = {}".format(relfilenode))
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assert c.fetchone()[0] > 0, "No buffers cached for the test relation"
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c.execute(
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"select reltablespace, reldatabase, relfilenode from pg_buffercache where relfilenode = {}"
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.format(relfilenode))
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reln = c.fetchone()
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log.info("Clear buffer cache to ensure no stale pages are brought into the cache")
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c.execute("select clear_buffer_cache()")
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c.execute(
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"select count(*) from pg_buffercache where relfilenode = {}".format(relfilenode))
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assert c.fetchone()[0] == 0, "Failed to clear buffer cache"
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log.info("Cache is clear, reading stale page version")
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn('foo', 'main', 0, '{}'))"
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.format(first[0]))
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direct_first = c.fetchone()
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assert first == direct_first, "Failed fetch page at historic lsn"
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c.execute(
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"select count(*) from pg_buffercache where relfilenode = {}".format(relfilenode))
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assert c.fetchone()[0] == 0, "relation buffers detected after invalidation"
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log.info("Cache is clear, reading latest page version without cache")
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn('foo', 'main', 0, NULL))"
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)
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direct_latest = c.fetchone()
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assert second == direct_latest, "Failed fetch page at latest lsn"
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c.execute(
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"select count(*) from pg_buffercache where relfilenode = {}".format(relfilenode))
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assert c.fetchone()[0] == 0, "relation buffers detected after invalidation"
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log.info(
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"Cache is clear, reading stale page version without cache using relation identifiers"
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)
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn( {}, {}, {}, 0, 0, '{}' ))"
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.format(reln[0], reln[1], reln[2], first[0]))
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direct_first = c.fetchone()
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assert first == direct_first, "Failed fetch page at historic lsn using oid"
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log.info(
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"Cache is clear, reading latest page version without cache using relation identifiers"
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)
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn( {}, {}, {}, 0, 0, NULL ))"
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.format(reln[0], reln[1], reln[2]))
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direct_latest = c.fetchone()
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assert second == direct_latest, "Failed fetch page at latest lsn"
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c.execute('drop table foo;')
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log.info(
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"Relation dropped, attempting reading stale page version without cache using relation identifiers"
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)
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn( {}, {}, {}, 0, 0, '{}' ))"
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.format(reln[0], reln[1], reln[2], first[0]))
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direct_first = c.fetchone()
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assert first == direct_first, "Failed fetch page at historic lsn using oid"
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log.info("Validation page inspect won't allow reading pages of dropped relations")
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try:
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c.execute("select * from page_header(get_raw_page('foo', 'main', 0));")
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assert False, "query should have failed"
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except UndefinedTable as e:
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log.info("Caught an expected failure: {}".format(e))
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def test_read_validation_neg(zenith_simple_env: ZenithEnv):
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env = zenith_simple_env
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env.zenith_cli.create_branch("test_read_validation_neg", "empty")
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pg = env.postgres.create_start("test_read_validation_neg")
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log.info("postgres is running on 'test_read_validation_neg' branch")
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with closing(pg.connect()) as con:
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with con.cursor() as c:
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for e in extensions:
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c.execute("create extension if not exists {};".format(e))
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log.info("read a page of a missing relation")
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try:
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn('Unknown', 'main', 0, '0/0'))"
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)
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assert False, "query should have failed"
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except UndefinedTable as e:
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log.info("Caught an expected failure: {}".format(e))
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c.execute("create table foo (c int) with (autovacuum_enabled = false)")
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c.execute("insert into foo values (1)")
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log.info("read a page at lsn 0")
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try:
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn('foo', 'main', 0, '0/0'))"
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)
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assert False, "query should have failed"
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except IoError as e:
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log.info("Caught an expected failure: {}".format(e))
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log.info("Pass NULL as an input")
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expected = (None, None, None)
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn(NULL, 'main', 0, '0/0'))"
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)
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assert c.fetchone() == expected, "Expected null output"
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn('foo', NULL, 0, '0/0'))"
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)
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assert c.fetchone() == expected, "Expected null output"
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn('foo', 'main', NULL, '0/0'))"
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)
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assert c.fetchone() == expected, "Expected null output"
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# This check is currently failing, reading beyond EOF is returning a 0-page
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log.info("Read beyond EOF")
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c.execute(
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"select lsn, lower, upper from page_header(get_raw_page_at_lsn('foo', 'main', 1, NULL))"
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)
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