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@Mytherin
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@qoega
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qoega commented May 23, 2025

Is the cache for external files dropped between queries? Cold result for every query should not have anything cached.

@Mytherin
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Mytherin commented May 23, 2025

Yes, the caches are in-memory only and the database is fully shut down and restarted between every query. See the run script. Note that duckdb is the full database, not just a client that connects to a database server.

DuckDB is one of the few databases that has full cold runs in ClickBench. Most other systems only reset OS buffers but leave the database server alive together with any caches that exist in the server.

[0.121,0.004,0.004],
[0.118,0.005,0.005],
[0.116,0.006,0.006]
[0.047,0.001,0.000],
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My local measurements:

[0.053,0.001,0.000],
[0.305,0.003,0.004],
[0.736,0.017,0.017],
[1.035,0.028,0.028],
[1.041,0.293,0.287],
[1.100,0.287,0.285],
[0.198,0.009,0.011],
[0.348,0.004,0.004],
[1.395,0.355,0.352],
[2.733,0.480,0.475],
[1.357,0.064,0.056],
[1.985,0.070,0.062],
[1.503,0.296,0.299],
[2.663,0.566,0.560],
[1.826,0.317,0.318],
[0.758,0.354,0.350],
[2.642,0.782,0.775],
[2.388,0.521,0.532],
[5.364,1.346,1.360],
[0.343,0.004,0.003],
[11.277,0.505,0.503],
[12.874,0.481,0.463],
[20.612,0.734,0.741],
[1.064,0.091,0.088],
[0.264,0.029,0.019],
[0.225,0.020,0.023],
[0.323,0.027,0.017],
[11.939,0.388,0.390],
[10.091,9.212,9.251],
[0.682,0.023,0.022],
[4.406,0.260,0.261],
[7.226,0.316,0.318],
[6.231,1.721,1.776],
[11.349,1.738,1.750],
[11.371,1.817,1.814],
[0.726,0.407,0.408],
[0.146,0.026,0.023],
[0.125,0.009,0.007],
[0.122,0.012,0.012],
[0.196,0.053,0.043],
[0.137,0.005,0.004],
[0.117,0.005,0.004],
[0.105,0.006,0.005],

are roughly in the same ballpark as @Mytherin's measurements. 👍

@rschu1ze rschu1ze merged commit aec53ea into ClickHouse:main May 26, 2025
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3 participants