New: use a subquery to interpret IN literals requiring data rep tra…

…nsformation.

- With the previous method, very long queries such as `ANY (ARRAY[test.color('000100'), test.color('CAFE12'), test.color('01E240'), ...` could be generated. Consider the case where the parser function name is 45 characters and there's a hundred literals. That's 4.5kB of SQL just for the function name alone!
- New version uses `unnest`: `ANY (SELECT test.color(unnest('{000100,CAFE12,01E240,...}'::text[]))` to produce a much shorter query.
- This is likely to be more performant and either way much more readable and debuggable in the logs.

src/PostgREST/Query/SqlFragment.hs

@@ -297,8 +297,10 @@ pgFmtUnknownLiteralForField value _ = value
 
 -- | Array version of the above, used by ANY().
 pgFmtArrayLiteralForField :: [Text] -> CoercibleField -> SQL.Snippet
-pgFmtArrayLiteralForField values CoercibleField{cfTransform=(Just parserProc)} = SQL.sql "ARRAY[" <> intercalateSnippet ", " (pgFmtCallUnary parserProc . unknownLiteral <$> values) <> "]"
--- When no transformation is requested, use an array literal which should be simpler, maybe faster.
+-- When a transformation is requested, we need to apply the transformation to each element of the array. This could be done by just making a query with `parser(value)` for each value, but may lead to huge query lengths. Imagine `data_representations.color_from_text('...'::text)` for repeated for a hundred values. Instead we use `unnest()` to unpack a standard array literal and then apply the transformation to each element, like a map.
+-- Note the literals will be treated as text since in every case when we use ANY() the parameters are textual (coming from a query string). We want to rely on the `text->domain` parser to do the right thing.
+pgFmtArrayLiteralForField values CoercibleField{cfTransform=(Just parserProc)} = SQL.sql "(SELECT " <> pgFmtCallUnary parserProc (SQL.sql "unnest(" <> unknownLiteral (pgBuildArrayLiteral values) <> "::text[])") <> ")"
+-- When no transformation is requested, we don't need a subquery.
 pgFmtArrayLiteralForField values _ = unknownLiteral (pgBuildArrayLiteral values)
 
 pgFmtFilter :: QualifiedIdentifier -> CoercibleFilter -> SQL.Snippet