fix(snowflake): only compile sample to TABLESAMPLE on physical tables
#10218
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jcrist
commented
Sep 25, 2024
| pytest.mark.notimpl( | ||
| ["snowflake"], | ||
| raises=SnowflakeProgrammingError, | ||
| reason="SAMPLE clause on views only supports row wise sampling without seed.", |
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This error message was a bit confusing to me. I initially thought it was saying "SAMPLE on subqueries with no seed only works row wise" (implying that if a seed was set, then block wise would work), but actualy it means "SAMPLE on subqueries only works row wise with no seed"
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Sep 25, 2024
| # Snowflake's TABLESAMPLE _can_ work on subqueries, but only by row and without | ||
| # a seed. This is effectively the same as `t.filter(random() <= fraction)`, and | ||
| # using TABLESAMPLE here would almost certainly have no benefit over the filter | ||
| # version in the optimized physical plan. To avoid a special case just for |
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Just curious, what is the special case here?
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In #10207 an xpassing test for snowflake was introduced. Instead of fixing the test marker, this expands our support for
samplein snowflake by only compiling it toTABLESAMPLEon physical tables. Snowflake'sTABLESAMPLEdoes work on subqueries, but only ifmethod="row"andseed=None. At the physical plan this should be identical to filter withrandom; I don't anticipate a perf difference here (and it's a lot easier to avoid adding a snowflake-specific rule to handle this case).