Hello All, I am learning at this point how index works in DBMS. So I am looking for a very broad explanation to clear my basics. I have an index defined "inspector_tool_idx4_1" UNIQUE, btree (company_id, item_code, deleted_at). Now I am using the *company_id* column in the where clause, and the selecting just the *item_code* field for all matching rows. I expected here the planner will do a index only scans. But it is doing bitmap index scan. Any idea what it is not doing what I expected it to do. inspection_development=# explain analyze select item_code from inspector_tool_components where company_id = '7881ff2e-0557-4734-9da8-2d33072ff1ef'; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------- Bitmap Heap Scan on inspector_tool_components (cost=45.92..1360.48 rows=1226 width=8) (actual time=0.382..1.202 rows=1232 loops=1) Recheck Cond: (company_id = '7881ff2e-0557-4734-9da8-2d33072ff1ef'::uuid) Heap Blocks: exact=81 -> Bitmap Index Scan on inspector_tool_idx4_1 (cost=0.00..45.61 rows=1226 width=0) (actual time=0.347..0.347 rows=1232 loops=1) Index Cond: (company_id = '7881ff2e-0557-4734-9da8-2d33072ff1ef'::uuid) Planning time: 0.207 ms Execution time: 1.358 ms (7 rows) |
