golang-migrate / migrate / 31292342710

55%

master: 55%

Pull #1424

github

perf(source): build migrations index lazily to avoid quadratic startup

Migrations.Append rebuilt and re-sorted the whole index on every call,
making source driver initialization O(n^2 log n) in the number of
migration files. All in-memory source drivers (file, iofs, aws_s3,
github, ...) call Append in a loop at Open/Init time, so startup cost
grew quadratically: 81ms at 1,000 migrations, 2.2s at 5,000 and 11.3s
at 10,000 on an i9-9900K.

Append now only marks the index dirty; the index is rebuilt at most
once, on the first read access (First/Prev/Next). No exported API
changes.

BenchmarkAppend5000 drops from ~2.2s/op to ~2ms/op.

8 of 8 new or added lines in 1 file covered. (100.0%)

4422 of 8053 relevant lines covered (54.91%)

18244.84 hits per line