Currently pg_stat_statements replaces constant values with ? characters. I've seen this be a problem on multiple occasions, in particular since it conflicts with the use of ? as an operator.
I'd like to propose changing the replacement character from ? to instead be a parameter (like $1).
My main motiviation is to aid external tools that parse pg_stat_statements output (like [0]), and currently have to resort to complex parser patches to distinguish operators from replacement characters.
First of all, attached 0001_pgss_additional_regression_tests.v1.patch which increases regression test coverage for a few scenarios relevant to this discussion.
Then, there is two variants I've prepared, only one of the two to be committed:
A) 0002_pgss_mask_with_incrementing_params.v1.patch: Replace constants with $1, $2, $3 (etc) in the normalized query, whilst respecting any existing params in the counting
B) 0003_pgss_mask_with_zero_param.v1.patch: Replace constants with $0 in the normalized query
Ideally I'd see A turn into something we can commit, but it involves a bit more computation to get the parameter numbers right. The benefit is that we could use PREPARE/EXECUTE with pg_stat_statements output.
B is intentionally simple, and would address the primary issue at hand (distinguishing from the ? operator).
I'm also adding this patch to the commitfest starting tomorrow.
Best,
Lukas
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