| From: | Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> |
|---|---|
| To: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Avoid displaying unnecessary "Recheck Cond" in EXPLAIN ANALYZE output if the bitmap is non-lossy |
| Date: | 2020-08-24 10:36:27 |
| Message-ID: | CALj2ACV36FXjVFWxKgxPr6ah1h0mdpcjz5G2DULONX0cGzXEDg@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi,
As specified in $subject, if the bitmap constructed by bitmap index
scan is non-lossy i.e. row-level bitmap, then showing "Recheck Cond"
in EXPLAIN ANALYZE output is pointless. However in EXPLAIN without
ANALYZE we can't say the bitmap is actually a non-lossy one, as we
don't actually construct the "original" bitmap, so showing "Recheck
Cond" in this case makes sense.
Attaching a small patch that corrects EXPLAIN ANALYZE output for bitmap scans.
Note: $subject is identified in [1].
Thoughts?
[1] - https://www.youtube.com/watch?v=UXKYAZOWDgk ---> at 13:50 (mm:ss)
With Regards,
Bharath Rupireddy.
EnterpriseDB: http://www.enterprisedb.com
| Attachment | Content-Type | Size |
|---|---|---|
| v1-Avoid-displaying-unnecessary-Recheck-Cond-when-th.patch | application/x-patch | 10.5 KB |
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