Hello,
I set enable_seqscan=off and also accidentally dropped the only index
on a table (actually, drop extension pg_bigm cascade) and observe
following:
postgres=# explain select * from testdata where name like '%gi%';
QUERY PLAN
On Mon, May 27, 2013 at 12:42 AM, Amit Langote amitlangot...@gmail.com wrote:
I set enable_seqscan=off and also accidentally dropped the only index
[...]
Seq Scan on testdata (cost=100.00..101.10 rows=2 width=71)
[...]
Although, I suspect the (dropped index + enable_seqscan)
2013/5/27 Amit Langote amitlangot...@gmail.com
Although, I suspect the (dropped index + enable_seqscan) causes this,
is the cost shown in explain output some kind of default max or
something like that for such abnormal cases?
When one uses “enable_” settings to adjust planner behavior,
Although, I suspect the (dropped index + enable_seqscan) causes this,
is the cost shown in explain output some kind of default max or
something like that for such abnormal cases?
When you set enable_xxx=off, it not actually disables the xxx
operation, it sets the start cost to the high value
When one uses “enable_” settings to adjust planner behavior, PostgreSQL
just sets really high costs for the operations affected (like the one you
see).
As SeqScan is the only possible way to execute your query, it is still
choosen.
I get it. Thanks!
--
Amit Langote
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