Performance improvement after output refactoring #89
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Removing pretty-print branching replaced several appendStringInfoString uses with appendStringInfo, which dramatically cleaned up the output code at the cost of decoding about 22% slower. We can recover most of this performance and keep the tidiness by adding a helper function to run appendStringInfoString for a variable number of strings. We lose some niceties of the sprintf-style template, but the performance seems worth it for high-throughput databases. "22% slower" was measured by populating a pgbench database with scale factor 5, running 50K transactions, DELETE-ing all the data, then timing how long it takes to receive all the changes with `pg_recvlogical`. On a c5.4xlarge EC2 instance backed by a gp2 EBS volume, this takes about 9.2 seconds on this branch compared to about 11.2s on master as of aa4077a.
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I ran some additional benchmarks overnight with the same script to verify the performance delta, and it remains consistent.
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@eulerto: this looks interesting. Thoughts? |
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In an attempt to bring our fork closer to master, we discovered that d4c0e81 introduced a meaningful performance change. d4c0e81 replaced several appendStringInfoString uses with appendStringInfo, which dramatically cleaned up the output code at the cost of a performance hit.
This proposal reduces decoding time by ~20% as measured by this benchmarking script. It swaps
appendStringInfofor a newappendStringInfoStringshelper, which loops through a variable argument list and calls the more performantappendStringInfoStringunder the hood, skipping if the argument starts with a null byte, i.e. whitespace args whenpretty-printisn't set. (I think this is safe in these use cases, and it is responsible for a full quarter of the performance return.)I'm very open to suggestions or other approaches that keep the (very nice) output refactoring and reclaim most of the performance.