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sql/(plan,analyzer): implement pushdown of filters and cols #86
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erizocosmico
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| if len(tables) == 1 { | ||
| filtersByTable[tables[0]] = append(filtersByTable[tables[0]], expr) |
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I believe I don't understand this logic. Does it mean that the expression is only added to the left table?
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A filter is only pushed down if only one table is mentioned in the expression (unless we want to change that behavior)
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Updated to receive sessions |
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ajnavarro
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mcarmonaa
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Signed-off-by: Miguel Molina <miguel@erizocosmi.co>
Signed-off-by: Miguel Molina <miguel@erizocosmi.co>
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Depends on #82
Closes #27
Closes #28
Supersedes #83
Implementation details
Only columns and filters that apply to a column are pushed down to that column. That is, if you have
42 > 5that filter will not be pushed down to any table, and if you havea.foo = 5that filter will only be pushed down to tablea.If more than one table is mentioned in a filter, it's not pushed down to neither. E.g.
a.foo = b.foois not pushed down.Perhaps we want the opposite and we want all filters pushed down to the table, regardless of whether it mentions the table or not?
Also, join conditions are not being pushed down as filters, should we also push those down?