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)
Thanks,
Arup Rakshit
a...@zeit.io
