Now trait `StringComparison` is a `BinaryExpression`. In fact, it should be a `BinaryPredicate`.
By making `StringComparison` as `BinaryPredicate`, we can throw error when a `expressions.Predicate` can't translate to a data source `Filter` in function `selectFilters`.
Without this modification, because we will wrap a `Filter` outside the scanned results in `pruneFilterProjectRaw`, we can't detect about something is wrong in translating predicates to filters in `selectFilters`.
The unit test of #5285 demonstrates such problem. In that pr, even `expressions.Contains` is not properly translated to `sources.StringContains`, the filtering is still performed by the `Filter` and so the test passes.
Of course, by doing this modification, all `expressions.Predicate` classes need to have its data source `Filter` correspondingly.
There is a small bug in `FilteredScanSuite` for doing `StringEndsWith` filter. This pr also fixes it.
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#5309 from viirya/translate_predicate and squashes the following commits:
b176385 [Liang-Chi Hsieh] Address comment.
275a493 [Liang-Chi Hsieh] More properly test for StringStartsWith, StringEndsWith and StringContains.
caf2347 [Liang-Chi Hsieh] Make trait StringComparison as BinaryPredicate and throw error when Predicate can't translate to data source Filter.
26b415e159