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## Problem PR https://github.com/neondatabase/neon/pull/6935 introduced a new function in neon extension: approximate_working_set_size This test case verifies its working correctly. --------- Co-authored-by: Alexander Bayandin <alexander@neon.tech>
75 lines
3.2 KiB
Python
75 lines
3.2 KiB
Python
from pathlib import Path
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from fixtures.log_helper import log
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from fixtures.neon_fixtures import NeonEnv
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from fixtures.utils import query_scalar
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def test_lfc_working_set_approximation(neon_simple_env: NeonEnv):
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env = neon_simple_env
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cache_dir = Path(env.repo_dir) / "file_cache"
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cache_dir.mkdir(exist_ok=True)
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branchname = "test_approximate_working_set_size"
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env.neon_cli.create_branch(branchname, "empty")
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log.info(f"Creating endopint with 1MB shared_buffers and 64 MB LFC for branch {branchname}")
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endpoint = env.endpoints.create_start(
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branchname,
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config_lines=[
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"shared_buffers='1MB'",
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f"neon.file_cache_path='{cache_dir}/file.cache'",
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"neon.max_file_cache_size='128MB'",
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"neon.file_cache_size_limit='64MB'",
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],
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)
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cur = endpoint.connect().cursor()
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cur.execute("create extension neon")
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log.info(f"preparing some data in {endpoint.connstr()}")
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ddl = """
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CREATE TABLE pgbench_accounts (
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aid bigint NOT NULL,
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bid integer,
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abalance integer,
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filler character(84),
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-- more web-app like columns
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text_column_plain TEXT DEFAULT repeat('NeonIsCool', 5),
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jsonb_column_extended JSONB DEFAULT ('{ "tell everyone": [' || repeat('{"Neon": "IsCool"},',9) || ' {"Neon": "IsCool"}]}')::jsonb
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)
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WITH (fillfactor='100');
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"""
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cur.execute(ddl)
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# prepare index access below
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cur.execute(
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"ALTER TABLE ONLY pgbench_accounts ADD CONSTRAINT pgbench_accounts_pkey PRIMARY KEY (aid)"
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)
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cur.execute(
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"insert into pgbench_accounts(aid,bid,abalance,filler) select aid, (aid - 1) / 100000 + 1, 0, '' from generate_series(1, 100000) as aid;"
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)
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# ensure correct query plans and stats
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cur.execute("vacuum ANALYZE pgbench_accounts")
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# determine table size - working set should approximate table size after sequential scan
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pages = query_scalar(cur, "SELECT relpages FROM pg_class WHERE relname = 'pgbench_accounts'")
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log.info(f"pgbench_accounts has {pages} pages, resetting working set to zero")
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cur.execute("select approximate_working_set_size(true)")
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cur.execute(
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'SELECT count(*) FROM pgbench_accounts WHERE abalance > 0 or jsonb_column_extended @> \'{"tell everyone": [{"Neon": "IsCool"}]}\'::jsonb'
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)
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# verify working set size after sequential scan matches table size and reset working set for next test
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blocks = query_scalar(cur, "select approximate_working_set_size(true)")
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log.info(f"working set size after sequential scan on pgbench_accounts {blocks}")
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assert pages * 0.8 < blocks < pages * 1.2
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# run a few point queries with index lookup
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cur.execute("SELECT abalance FROM pgbench_accounts WHERE aid = 4242")
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cur.execute("SELECT abalance FROM pgbench_accounts WHERE aid = 54242")
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cur.execute("SELECT abalance FROM pgbench_accounts WHERE aid = 104242")
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cur.execute("SELECT abalance FROM pgbench_accounts WHERE aid = 204242")
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# verify working set size after some index access of a few select pages only
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blocks = query_scalar(cur, "select approximate_working_set_size(true)")
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log.info(f"working set size after some index access of a few select pages only {blocks}")
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assert blocks < 10
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