internal/codegen: cache pattern matching compilations #2028
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Type overrides are checked linearly for every codegen'd type reference. That linear check currently compiles a regexp pattern for every override that's considered (multiple times, actually). This commit adds a simple memoizing cache so that each pattern is only ever compiled once. This dramatically improves performance of sqlc for users who have many overrides. ngrok's usage of sqlc generate sees a 10x speedup from this change (4s -> 0.4s).
I haven't profiled the memory tradeoff here but I expect it's negligible.