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c76a0cff68
Make `partialize_agg()` support parallel query execution. To make this work, the finalize node need combine the individual partials from each parallel worker, but the final step that turns the resulting partial into the finished aggregate should not happen. Thus, in the case of distributed hypertables, each data node can run a parallel query to compute a partial, and the access node can later combine and finalize these partials into the final aggregate. Esssentially, there will be one combine step (minus final) on each data node, and then another one plus final on the access node. To implement this, the finalize aggregate plan is simply modified to elide the final step, and to reserialize the partial. It is only possible to do this at the plan stage; if done at the path stage, the PostgreSQL planner will hit assertions that assume that the node has certain values (e.g., it doesn't expect combine Paths to skip the final step).
26 lines
1.4 KiB
SQL
26 lines
1.4 KiB
SQL
-- This file and its contents are licensed under the Apache License 2.0.
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-- Please see the included NOTICE for copyright information and
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-- LICENSE-APACHE for a copy of the license.
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CREATE OR REPLACE FUNCTION _timescaledb_internal.partialize_agg(arg ANYELEMENT)
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RETURNS BYTEA AS '@MODULE_PATHNAME@', 'ts_partialize_agg' LANGUAGE C STABLE PARALLEL SAFE;
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CREATE OR REPLACE FUNCTION _timescaledb_internal.finalize_agg_sfunc(
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tstate internal, aggfn TEXT, inner_agg_collation_schema NAME, inner_agg_collation_name NAME, inner_agg_input_types NAME[][], inner_agg_serialized_state BYTEA, return_type_dummy_val ANYELEMENT)
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RETURNS internal
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AS '@MODULE_PATHNAME@', 'ts_finalize_agg_sfunc'
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LANGUAGE C IMMUTABLE;
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CREATE OR REPLACE FUNCTION _timescaledb_internal.finalize_agg_ffunc(
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tstate internal, aggfn TEXT, inner_agg_collation_schema NAME, inner_agg_collation_name NAME, inner_agg_input_types NAME[][], inner_agg_serialized_state BYTEA, return_type_dummy_val ANYELEMENT)
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RETURNS anyelement
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AS '@MODULE_PATHNAME@', 'ts_finalize_agg_ffunc'
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LANGUAGE C IMMUTABLE;
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CREATE OR REPLACE AGGREGATE _timescaledb_internal.finalize_agg(agg_name TEXT, inner_agg_collation_schema NAME, inner_agg_collation_name NAME, inner_agg_input_types NAME[][], inner_agg_serialized_state BYTEA, return_type_dummy_val anyelement) (
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SFUNC = _timescaledb_internal.finalize_agg_sfunc,
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STYPE = internal,
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FINALFUNC = _timescaledb_internal.finalize_agg_ffunc,
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FINALFUNC_EXTRA
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);
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