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Postgres knows whether a given aggregate is parallel-safe, and creates parallel aggregation plans based on that. The `partialize_agg` is a wrapper we use to perform partial aggregation on data nodes. It is a pure function that produces serialized aggregation state as a result. Being pure, it doesn't influence parallel safety. This means we don't need to mark it parallel-unsafe to artificially disable the parallel plans for partial aggregation. They will be chosen as usual based on the parallel-safety of the underlying aggregate function.
42 lines
1.8 KiB
SQL
42 lines
1.8 KiB
SQL
-- This file and its contents are licensed under the Timescale License.
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-- Please see the included NOTICE for copyright information and
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-- LICENSE-TIMESCALE for a copy of the license.
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-- Test that for parallel-safe aggregate function a parallel plan is generated
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-- on data nodes, and for unsafe it is not. We use a manually created safe
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-- function and not a builtin one, to check that we can in fact create a
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-- function that is parallelized, to prevent a false negative (i.e. it's not
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-- parallelized, but for a different reason, not because it's unsafe).
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-- Create a relatively big table on one data node to test parallel plans and
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-- avoid flakiness.
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create table metrics_dist1(like metrics_dist);
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select table_name from create_distributed_hypertable('metrics_dist1', 'time', 'device_id',
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data_nodes => '{"data_node_1"}');
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insert into metrics_dist1 select * from metrics_dist order by metrics_dist limit 20000;
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\set safe 'create or replace aggregate ts_debug_shippable_safe_count(*) (sfunc = int8inc, combinefunc=int8pl, stype = bigint, initcond = 0, parallel = safe);'
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\set unsafe 'create or replace aggregate ts_debug_shippable_unsafe_count(*) (sfunc = int8inc, combinefunc=int8pl, stype = bigint, initcond = 0, parallel = unsafe);'
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:safe
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call distributed_exec(:'safe');
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:unsafe
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call distributed_exec(:'unsafe');
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call distributed_exec($$ set parallel_tuple_cost = 0; $$);
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call distributed_exec($$ set parallel_setup_cost = 0; $$);
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call distributed_exec($$ set max_parallel_workers_per_gather = 1; $$);
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set timescaledb.enable_remote_explain = 1;
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set enable_partitionwise_aggregate = 1;
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\set analyze 'explain (analyze, verbose, costs off, timing off, summary off)'
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:analyze
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select count(*) from metrics_dist1;
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:analyze
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select ts_debug_shippable_safe_count(*) from metrics_dist1;
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:analyze
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select ts_debug_shippable_unsafe_count(*) from metrics_dist1; |