Compression for Memory tables#20168
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alexey-milovidov merged 30 commits intomasterfrom Feb 20, 2021
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There is up to 5 times improvement in perf tests. |
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Broken after merging NuRaft. |
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OOM |
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I found another case how It happens due do dynamic block size selection. |
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Experiment with compressing into arenas: https://github.com/ClickHouse/ClickHouse/compare/in-memory-compression-arenas?expand=1 |
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@amosbird If we lower block size to 8192 for this Memory table, query will be faster - about 30 ms if I remember correctly. |
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This PR looks ready but I cannot enable compression by default:
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compresssetting forMemorytables. If it's enabled the table will use less RAM. On some machines and datasets it can also work faster on SELECT, but it is not always the case. This closes #20093. Note: there are reasons why Memory tables can work slower than MergeTree: (1) lack of compression (2) static size of blocks (3) lack of indices and prewhere...