quantizer: group named parameters in SQL query

[MDrollette]

Many SQL libraries use named parameters when building queries. This results in queries that look like this when they are pulled from the library and sent in the trace:

SELECT * FROM sale_fee LEFT JOIN fee_type ON ( sale_fee.fee_type_id = fee_type.id ) 
WHERE sale_fee.sale_code = :p1 AND fee_type.fee_calculation_type IN ( :p2, :p3, :p4, :p5 )

It seems like it would be possible to translate these named parameters to regular ? placeholders, and then apply the normal filtering/grouping rules to them in order to reduce cardinality. Named params can be identified by the colon prefix.

SELECT * FROM sale_fee LEFT JOIN fee_type ON ( sale_fee.fee_type_id = fee_type.id ) 
WHERE sale_fee.sale_code = ? AND fee_type.fee_calculation_type IN ( ? )

[CAFxX]

A similar problem we are seeing right now in Mercari, that seems to be partially implied by the description above, is that even multiple unnamed placeholders in IN() are not merged. E.g. optionally I would something like the following (that is common when you have endpoints that accept a variable number of objects):

SELECT * FROM table WHERE id IN (?, ?, ?, ?)
SELECT * FROM table WHERE id IN (?, ?, ?, ?, ?)
SELECT * FROM table WHERE id IN (?, ?, ?, ?, ?, ?)

to be presented as:

SELECT * FROM table WHERE id IN (?)

(or maybe IN (??), to signify that multiple placeholders have been merged?)

This would help to avoid this, that is not particularly helpful: