[Tile-serving] [osm2pgsql-dev/osm2pgsql] Add grouped-linemerge generalization (PR #2482)

[Sarah Hoffmann]

@lonvia commented on this pull request.



> +    }
+}
+
+void gen_grouped_linemerge_t::process_create()
+{
+    if (get_params().get_bool("create_indexes", true)) {
+        log_gen("Creating endpoint indexes on source table...");
+        dbexec(
+            R"(CREATE INDEX IF NOT EXISTS "{idx_startpt}" ON {src} USING btree)"
+            R"( (ST_X(ST_StartPoint("{geom_column}")),)"
+            R"( ST_Y(ST_StartPoint("{geom_column}"))) {index_predicate})");
+        dbexec(
+            R"(CREATE INDEX IF NOT EXISTS "{idx_endpt}" ON {src} USING btree)"
+            R"( (ST_X(ST_EndPoint("{geom_column}")),)"
+            R"( ST_Y(ST_EndPoint("{geom_column}"))) {index_predicate})");
+    }

Ah, I thought the main performance loss was because of the relatively large bboxes for ways. A gist of points wouldn't have that problem. But I wouldn't be surprised if gist is slower overall.

Is it possible to put a ST_Point in a btree and get equality comparison? That would give you the best of both worlds.

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