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https://github.com/ClickHouse/ClickHouse.git
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44 lines
1.2 KiB
SQL
44 lines
1.2 KiB
SQL
DROP TABLE IF EXISTS t_modify_from_lc_1;
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DROP TABLE IF EXISTS t_modify_from_lc_2;
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SET allow_suspicious_low_cardinality_types = 1;
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CREATE TABLE t_modify_from_lc_1
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(
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id UInt64,
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a LowCardinality(UInt32) CODEC(NONE)
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)
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ENGINE = MergeTree ORDER BY tuple()
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SETTINGS min_bytes_for_wide_part = 0;
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CREATE TABLE t_modify_from_lc_2
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(
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id UInt64,
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a LowCardinality(UInt32) CODEC(NONE)
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)
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ENGINE = MergeTree ORDER BY tuple()
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SETTINGS min_bytes_for_wide_part = 0;
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INSERT INTO t_modify_from_lc_1 SELECT number, number FROM numbers(100000);
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INSERT INTO t_modify_from_lc_2 SELECT number, number FROM numbers(100000);
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OPTIMIZE TABLE t_modify_from_lc_1 FINAL;
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OPTIMIZE TABLE t_modify_from_lc_2 FINAL;
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ALTER TABLE t_modify_from_lc_1 MODIFY COLUMN a UInt32;
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-- Check that dictionary of LowCardinality is actually
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-- dropped and total size on disk is reduced.
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WITH groupArray((table, bytes))::Map(String, UInt64) AS stats
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SELECT
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length(stats), stats['t_modify_from_lc_1'] < stats['t_modify_from_lc_2']
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FROM
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(
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SELECT table, sum(bytes_on_disk) AS bytes FROM system.parts
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WHERE database = currentDatabase() AND table LIKE 't_modify_from_lc%' AND active
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GROUP BY table
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);
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DROP TABLE IF EXISTS t_modify_from_lc_1;
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DROP TABLE IF EXISTS t_modify_from_lc_2;
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