Re: Query RE: Optimising UUID Lookups

(1) SELECT uuid FROM lookup WHERE state = 200 LIMIT 4000;

OUTPUT FROM EXPLAIN (ANALYZE, BUFFERS):
------------------------------------------------
 Limit  (cost=0.00..4661.02 rows=4000 width=16) (actual
time=0.009..1.036 rows=4000 loops=1)
   Buffers: shared hit=42
   ->  Seq Scan on lookup  (cost=0.00..1482857.00 rows=1272559
width=16) (actual time=0.008..0.777 rows=4000 loops=1)
         Filter: (state = 200)
         Rows Removed by Filter: 410
         Buffers: shared hit=42
 Total runtime: 1.196 ms
(7 rows)

Question: Why does this do a sequence scan and not an index scan when
there is a btree on state?

(2) SELECT article_data.id, article_data.uuid, article_data.title,
article_data.text FROM article_data WHERE uuid = ANY
('{f0d5e665-4f21-4337-a54b-cf0b4757db65,..... 3999 more uuid's
....}'::uuid[]);


OUTPUT FROM EXPLAIN (ANALYZE, BUFFERS):
------------------------------------------------
 Index Scan using article_data_uuid_key on article_data
(cost=5.56..34277.00 rows=4000 width=581) (actual time=0.063..66029.031 rows=4000 loops=1)
   Index Cond: (uuid = ANY

​

(

​'...'

::uuid[]))

   Buffers: shared hit=16060

​​

read=4084 dirtied=292
 Total runtime: 66041.443 ms Question: