Merge pull request #71 from rustprooflabs/perf-notes

Performance notes

Author: rustprooflabs

PERFORMANCE.md

@@ -0,0 +1,56 @@
+# PgOSM-Flex Performance
+
+This page provides a rough guide of how PgOSM-Flex performance compares
+against the legacy osm2pgsql load.  **This comparison is apples to oranges** but
+is hopefully still helpful for planning.
+The data loaded via PgOSM-Flex is of much higher quality than the
+legacy three-table load.  Due to this fundamental switch, data loaded
+via PgOSM-Flex is ready-to-use as soon as the load is done...
+it does not require massive post-import cleanup!
+
+The current findings show a given region will take a few times longer using the
+full PgOSM-Flex (`run-all.lua`) than using the legacy method.
+
+> Note: The Flex output of osm2pgsql is currently **Experimental**
+and performance characteristics are likely to shift. 
+
+
+## Versions Tested
+
+Versions used for testing:
+
+* Ubuntu 20.04
+* osm2pgsql 1.4.0
+* PostgreSQL 13.1
+* PostGIS 3.1
+
+
+## Small sub-regions
+
+Small sub-regions test the District of Columbia and Colorado subregions from
+Geofabrik. PBF files were downloaded from Geofabrik in early January 2021.
+Tested multiple machines with 64 GB RAM, multiple CPUs and fast SSDs receiving
+consistent results.
+
+
+| Sub-region | Legacy (s) | Flex Compatible (s) | PgOSM-Flex Road/Place (s) | PgOSM-Flex No-Tags (s) | PgOSM-Flex All (s) |
+|    :---    |    :-:    |    :-:    |    :-:    |     :-:    |    :-:    |
+|    District of Columbia    |    6    |    10    |    6     |     21    |    28    |
+|    Colorado     |    62    |    90    |    72    |    217    |    270    |
+
+
+> Note: THe above timings for PgOSM-Flex loads only represent the `.lua` portion.  Running the associated `.sql` script for each load is relatively fast compared to the Lua portion.
+
+
+## Large regions
+
+Initial results on larger scale tests (both data and hardware) are available
+in [issue #12](https://github.com/rustprooflabs/pgosm-flex/issues/12).  As this project
+matures additional performance testing results will become available.
+
+## Legacy benchmarks
+
+See the blog post
+[Scaling osm2pgsql: Process and costs](https://blog.rustprooflabs.com/2019/10/osm2pgsql-scaling)
+for a deeper look at how performance scales using various sizes of regions and hardware.
+