Sorry Alex i forget mention that i have setscan of in my last test.
now I have set seqscan on and indexscan on and added order by _id
The table has an index in the _id field
CREATE INDEX i_documentcontent_document
ON t_documentcontent
USING btree
(_document);
The database was rencently vacum analyze , but not vacun full
here is the explain of 2 diferent queries , when i put a large OFFSET
EXPLAIN ANALYZE SELECT
t_documentcontent._id AS _id
FROM t_documentcontent ORDER BY _id LIMIT 50 OFFSET 50000
"Limit (cost=137068.24..137068.36 rows=50 width=58) (actual time=41119.702..41119.792 rows=50 loops=1)"
" -> Sort (cost=136943.24..137320.26 rows=150807 width=58) (actual time=41064.802..41100.424 rows=50050 loops=1)"
" Sort Key: _id"
" -> Seq Scan on t_documentcontent (cost= 0.00..110772.07 rows=150807 width=58) (actual time=106.679..33267.194 rows=150807 loops=1)"
"Total runtime: 41120.015 ms"
EXPLAIN ANALYZE SELECT
t_documentcontent._id AS _id
FROM t_documentcontent ORDER BY _id LIMIT 50 OFFSET 10000
"Limit (cost=39839.37..40038.56 rows=50 width=58) (actual time=1172.969..1194.228 rows=50 loops=1)"
" -> Index Scan using i_documentcontent_id on t_documentcontent (cost=0.00..600805.54 rows=150807 width=58) (actual time= 0.077..1189.688 rows=10050 loops=1)"
"Total runtime: 1194.316 ms"
Tom
i using uuid for the _id field that is the primary key add a WHERE id > ? don 't apply
the cursor aproach is also not suitable for same of my queries
I use this query for paginate contents of a filesysstem with lots of documents avoid offset is not posible always