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0b47f4a9e9
Consider the following example:
CREATE TABLE test(p DateTime, k int) ENGINE MergeTree PARTITION BY toDate(p) ORDER BY k;
INSERT INTO test VALUES ('2020-09-01 00:01:02', 1), ('2020-09-01 20:01:03', 2), ('2020-09-02 00:01:03', 3);
- SELECT count() FROM test WHERE toDate(p) >= '2020-09-01' AND p <= '2020-09-01 00:00:00'
In this case rpn will be (FUNCTION_IN_RANGE, FUNCTION_UNKNOWN (due to strict), FUNCTION_AND)
and for optimize_trivial_count_query we cannot use index if there is at least one FUNCTION_UNKNOWN.
since there is no post processing and return count() based on only the first predicate is wrong.
Before this patch FUNCTION_UNKNOWN was allowed for optimize_trivial_count_query, and the result was wrong.
And two examples above just to show the difference, the behaviour hadn't been changed with this patch:
- SELECT * FROM test WHERE toDate(p) >= '2020-09-01' AND p <= '2020-09-01 00:00:00'
In this case will be (FUNCTION_IN_RANGE, FUNCTION_IN_RANGE (due to non-strict), FUNCTION_AND)
so it will prune everything out and nothing will be read.
- SELECT * FROM test WHERE toDate(p) >= '2020-09-01' AND toUnixTimestamp(p)%5==0
In this case will be (FUNCTION_IN_RANGE, FUNCTION_UNKNOWN, FUNCTION_AND)
and all, two, partitions will be scanned, but due to filtering later none of rows will be matched.
38 lines
1.1 KiB
C++
38 lines
1.1 KiB
C++
#pragma once
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#include <unordered_map>
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#include <Storages/KeyDescription.h>
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#include <Storages/MergeTree/IMergeTreeDataPart.h>
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#include <Storages/MergeTree/KeyCondition.h>
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namespace DB
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{
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/// Pruning partitions in verbatim way using KeyCondition
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class PartitionPruner
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{
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private:
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std::unordered_map<String, bool> partition_filter_map;
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const KeyDescription & partition_key;
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KeyCondition partition_condition;
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bool useless;
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using DataPart = IMergeTreeDataPart;
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using DataPartPtr = std::shared_ptr<const DataPart>;
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public:
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PartitionPruner(const KeyDescription & partition_key_, const SelectQueryInfo & query_info, const Context & context, bool strict)
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: partition_key(partition_key_)
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, partition_condition(
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query_info, context, partition_key.column_names, partition_key.expression, true /* single_point */, strict)
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, useless(strict ? partition_condition.anyUnknownOrAlwaysTrue() : partition_condition.alwaysUnknownOrTrue())
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{
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}
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bool canBePruned(const DataPartPtr & part);
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bool isUseless() const { return useless; }
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};
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}
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