pg_query_go/v4 no longer accepts ? for input placeholders

[kyleconroy]

In the process of upgrading from v2 to v4 (sqlc-dev/sqlc#2114) I discovered a breaking change. In v2, the following query parses without an error:

SELECT * FROM users WHERE id = ?

However, in v4, this same query now returns a syntax error.

Is this a PostgreSQL change or pg_query_go change?

A full reproduction here: https://gist.github.com/kyleconroy/792b77389287f34a501e572b6c7281df

[lfittl]

@kyleconroy This change is intentional - that was always a libpg_query patch, Postgres never supported this syntax for parameter references. Though some ORMs support ? replacement characters, they then do local substitution and don't send the query in that form to the Postgres server.

The motivation for having this modified parser grammar in pg_query to begin with was that we wanted to be able to read the query texts produced by pg_stat_statements, which prior to Postgres 10 used ? (see the commit that changes this for reference).

Since those Postgres versions have reached end of life for over a year now, we decided to drop support for ? replacement characters, which also solves a few edge cases where it caused problems with operators containing ? (see e.g. pganalyze/libpg_query#132)

It sounds like this might be a problem for sqlc. Can you describe a bit more the use case for using ?? (are you doing local substitution of the values before sending them to Postgres?)

[kyleconroy]

Postgres never supported this syntax for parameter references

Okay, that's great news. sqlc does not do the parameter re-writing, so this shouldn't be a breaking change for users. While the parser allowed those placeholders, those queries never would have worked in the first place.