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ea0c97d590
Common time-series rollups are of the form SELECT date_trunc(const, time) as t, aggregates... GROUP BY t ORDER BY t DESC LIMIT const2. Previously, Postgres would not optimize such queries because it could not match date_trunc(const, time) to any indexes on time, since it has no way to know that a sort on time is always a valid sort on date_trunc(const, time). This commit implements this optimization for date_trunc but it could apply to a wider range of functions, to be implemented later.
34 lines
1.8 KiB
SQL
34 lines
1.8 KiB
SQL
\o /dev/null
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\ir include/insert_two_partitions.sql
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\o
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SELECT * FROM PUBLIC."two_Partitions";
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EXPLAIN (verbose ON, costs off) SELECT * FROM PUBLIC."two_Partitions";
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\echo "The following queries should NOT scan two_Partitions._hyper_1_1_0_partition"
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EXPLAIN (verbose ON, costs off) SELECT * FROM PUBLIC."two_Partitions" WHERE device_id = 'dev20';
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EXPLAIN (verbose ON, costs off) SELECT * FROM PUBLIC."two_Partitions" WHERE device_id = 'dev'||'20';
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EXPLAIN (verbose ON, costs off) SELECT * FROM PUBLIC."two_Partitions" WHERE 'dev'||'20' = device_id;
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--TODO: handle this later?
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--EXPLAIN (verbose ON, costs off) SELECT * FROM "two_Partitions" WHERE device_id IN ('dev20', 'dev21');
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\echo "The following shows non-aggregated queries with time desc using merge append"
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EXPLAIN (verbose ON, costs off)SELECT * FROM PUBLIC."two_Partitions" ORDER BY "timeCustom" DESC NULLS LAST limit 2;
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--shows that more specific indexes are used if the WHERE clauses "match", uses the series_1 index here.
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EXPLAIN (verbose ON, costs off)SELECT * FROM PUBLIC."two_Partitions" WHERE series_1 IS NOT NULL ORDER BY "timeCustom" DESC NULLS LAST limit 2;
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--here the "match" is implication series_1 > 1 => series_1 IS NOT NULL
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EXPLAIN (verbose ON, costs off)SELECT * FROM PUBLIC."two_Partitions" WHERE series_1 > 1 ORDER BY "timeCustom" DESC NULLS LAST limit 2;
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--note that without time transform things work too
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EXPLAIN (verbose ON, costs off)SELECT "timeCustom" t, min(series_0) FROM PUBLIC."two_Partitions" GROUP BY t ORDER BY t DESC NULLS LAST limit 2;
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--TODO: time transform doesn't work
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EXPLAIN (verbose ON, costs off)SELECT "timeCustom"/10 t, min(series_0) FROM PUBLIC."two_Partitions" GROUP BY t ORDER BY t DESC NULLS LAST limit 2;
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EXPLAIN (verbose ON, costs off)SELECT "timeCustom"%10 t, min(series_0) FROM PUBLIC."two_Partitions" GROUP BY t ORDER BY t DESC NULLS LAST limit 2;
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