Added order by to PostgreSQL and SQLite SQL queries in readStream to ensure messages ordering #241
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Based on the @dawidranda finding in #239, it seems that sometimes PostgreSQL event store is not returning events in the proper order. Emmett has an index on stream_id and stream position which is ascending, so when reading it's using the index and returning messages in right order. If it doesn't work for you then it probably means that for some reason Postgres is not using index. The potential reason is that maybe it only has rows from a single stream, and then it decides that doing full scan will be faster than using index. I wasn't able to reproduce on my local box the issues, even when adding tests simulating scenario described in #239, but adding ORDER BY won't do harm, as it should still use index, so we should not get the performance penalty. Fixes #239
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Based on the @dawidranda finding in #239, it seems that sometimes the PostgreSQL event store does not return events in the proper order.
Emmett has an index on stream_id and stream position, which is ascending, so when reading, it uses the index and returns messages in the right order.
If it doesn't work for you, it probably means that Postgres is not using an index for some reason. One potential reason is that it may only have rows from a single stream and then decide to do a full scan, which will be faster than using an index.
I wasn't able to reproduce the issues on my local box, even when adding tests simulating the scenario described in #239, but adding ORDER BY won't do harm, as it should still use the index, so we should not get the performance penalty. Plus relying on a certain query plan is not the smartest move.
Applied the same for SQLite implementation.
Fixes #239