mirror of https://github.com/citusdata/citus.git
wip
Sait Talha Nisanci
parent
4e3c6224fb
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eea210c9f5
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--
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-- MULTI_AGG_APPROXIMATE_DISTINCT
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--
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-- Create HLL extension if present, print false result otherwise
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SELECT CASE WHEN COUNT(*) > 0 THEN
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'CREATE EXTENSION HLL'
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ELSE 'SELECT false AS hll_present' END
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AS create_cmd FROM pg_available_extensions()
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WHERE name = 'hll'
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\gset
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:create_cmd;
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SET citus.coordinator_aggregation_strategy TO 'disabled';
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-- Try to execute count(distinct) when approximate distincts aren't enabled
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SELECT count(distinct l_orderkey) FROM lineitem;
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count
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---------------------------------------------------------------------
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2985
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(1 row)
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-- Check approximate count(distinct) at different precisions / error rates
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SET citus.count_distinct_error_rate = 0.1;
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SELECT count(distinct l_orderkey) FROM lineitem;
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count
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---------------------------------------------------------------------
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2612
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(1 row)
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SET citus.count_distinct_error_rate = 0.01;
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SELECT count(distinct l_orderkey) FROM lineitem;
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count
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---------------------------------------------------------------------
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2967
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(1 row)
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-- Check approximate count(distinct) for different data types
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SELECT count(distinct l_partkey) FROM lineitem;
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count
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---------------------------------------------------------------------
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11654
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(1 row)
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SELECT count(distinct l_extendedprice) FROM lineitem;
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count
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---------------------------------------------------------------------
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11691
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(1 row)
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SELECT count(distinct l_shipdate) FROM lineitem;
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count
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---------------------------------------------------------------------
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2483
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(1 row)
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SELECT count(distinct l_comment) FROM lineitem;
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count
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---------------------------------------------------------------------
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11788
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(1 row)
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-- Check that we can execute approximate count(distinct) on complex expressions
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SELECT count(distinct (l_orderkey * 2 + 1)) FROM lineitem;
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count
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---------------------------------------------------------------------
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2980
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(1 row)
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SELECT count(distinct extract(month from l_shipdate)) AS my_month FROM lineitem;
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my_month
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---------------------------------------------------------------------
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12
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(1 row)
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SELECT count(distinct l_partkey) / count(distinct l_orderkey) FROM lineitem;
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?column?
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---------------------------------------------------------------------
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3
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(1 row)
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-- Check that we can execute approximate count(distinct) on select queries that
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-- contain different filter, join, sort and limit clauses
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SELECT count(distinct l_orderkey) FROM lineitem
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WHERE octet_length(l_comment) + octet_length('randomtext'::text) > 40;
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count
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---------------------------------------------------------------------
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2355
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(1 row)
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SELECT count(DISTINCT l_orderkey) FROM lineitem, orders
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WHERE l_orderkey = o_orderkey AND l_quantity < 5;
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count
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---------------------------------------------------------------------
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835
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(1 row)
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SELECT count(DISTINCT l_orderkey) as distinct_order_count, l_quantity FROM lineitem
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WHERE l_quantity < 32.0
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GROUP BY l_quantity
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ORDER BY distinct_order_count ASC, l_quantity ASC
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LIMIT 10;
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distinct_order_count | l_quantity
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---------------------------------------------------------------------
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210 | 29.00
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216 | 13.00
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217 | 16.00
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219 | 3.00
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220 | 18.00
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222 | 14.00
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223 | 7.00
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223 | 17.00
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223 | 26.00
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223 | 31.00
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(10 rows)
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-- Check that approximate count(distinct) works at a table in a schema other than public
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-- create necessary objects
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SET citus.next_shard_id TO 20000000;
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SET citus.next_placement_id TO 20000000;
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CREATE SCHEMA test_count_distinct_schema;
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CREATE TABLE test_count_distinct_schema.nation_hash(
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n_nationkey integer not null,
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n_name char(25) not null,
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n_regionkey integer not null,
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n_comment varchar(152)
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);
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SELECT create_distributed_table('test_count_distinct_schema.nation_hash', 'n_nationkey', 'hash');
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create_distributed_table
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---------------------------------------------------------------------
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(1 row)
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\copy test_count_distinct_schema.nation_hash FROM STDIN with delimiter '|';
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SET search_path TO public;
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SET citus.count_distinct_error_rate TO 0.01;
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SELECT COUNT (DISTINCT n_regionkey) FROM test_count_distinct_schema.nation_hash;
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count
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---------------------------------------------------------------------
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3
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(1 row)
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-- test with search_path is set
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SET search_path TO test_count_distinct_schema;
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SELECT COUNT (DISTINCT n_regionkey) FROM nation_hash;
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count
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---------------------------------------------------------------------
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3
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(1 row)
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SET search_path TO public;
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-- If we have an order by on count(distinct) that we intend to push down to
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-- worker nodes, we need to error out. Otherwise, we are fine.
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SET citus.limit_clause_row_fetch_count = 1000;
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SELECT l_returnflag, count(DISTINCT l_shipdate) as count_distinct, count(*) as total
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FROM lineitem
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GROUP BY l_returnflag
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ORDER BY count_distinct
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LIMIT 10;
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ERROR: cannot approximate count(distinct) and order by it
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HINT: You might need to disable approximations for either count(distinct) or limit through configuration.
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SELECT l_returnflag, count(DISTINCT l_shipdate) as count_distinct, count(*) as total
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FROM lineitem
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GROUP BY l_returnflag
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ORDER BY total
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LIMIT 10;
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l_returnflag | count_distinct | total
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---------------------------------------------------------------------
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R | 1103 | 2901
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A | 1108 | 2944
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N | 1265 | 6155
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(3 rows)
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SELECT
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l_orderkey,
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count(l_partkey) FILTER (WHERE l_shipmode = 'AIR'),
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count(DISTINCT l_partkey) FILTER (WHERE l_shipmode = 'AIR'),
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count(DISTINCT CASE WHEN l_shipmode = 'AIR' THEN l_partkey ELSE NULL END)
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FROM lineitem
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GROUP BY l_orderkey
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ORDER BY 2 DESC, 1 DESC
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LIMIT 10;
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l_orderkey | count | count | count
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---------------------------------------------------------------------
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12005 | 4 | 4 | 4
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5409 | 4 | 4 | 4
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4964 | 4 | 4 | 4
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14848 | 3 | 3 | 3
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14496 | 3 | 3 | 3
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13473 | 3 | 3 | 3
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13122 | 3 | 3 | 3
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12929 | 3 | 3 | 3
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12645 | 3 | 3 | 3
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12417 | 3 | 3 | 3
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(10 rows)
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-- Check that we can revert config and disable count(distinct) approximations
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SET citus.count_distinct_error_rate = 0.0;
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SELECT count(distinct l_orderkey) FROM lineitem;
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count
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---------------------------------------------------------------------
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2985
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(1 row)
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