RE: Berkeley DB... - Mailing list pgsql-hackers

From Mikheev, Vadim
Subject RE: Berkeley DB...
Date
Msg-id 8F4C99C66D04D4118F580090272A7A23018C01@SECTORBASE1
Whole thread Raw
In response to Berkeley DB...  ("Mikheev, Vadim" <vmikheev@SECTORBASE.COM>)
Responses Re: Berkeley DB...
List pgsql-hackers
> Times for the insert loop:
> 14   MySQL-MyISAM
> 23   PostgreSQL (no fsync)
> 53   MySQL-BDB (with fsync -- don't know how to turn it off yet)

PostgreSQL 6.5.3; -B 16384; SUN Ultra10 with some IDE disk.

1. with fsync, all inserts in single transaction:     73 sec
2. with fsync, use COPY:                               3 sec
3. without fsync, use COPY:                            3 sec
4. without fsync, all inserts in single transaction:  71 sec
5. without fsync, each insert in own transaction:    150 sec

Do you see difference for INSERT/COPY in 1./2.? Shouldn't we try
to speed up our PARSER/PLANNER, keeping in mind that WAL will speed
up our storage sub-system?!

Also, 4. & 5. show that transaction begin/commit take too long time.
Could you run your test for all inserts in single transaction?

(If we want to test storage sub-system, let's do our test un-affected
by other ones...)

> The select:
> 0.75  MySQL-MyISAM
> 0.77  MySQL-BDB
> 2.43  PostgreSQL

select a from foo order by a

didn't use index in my case, so I've run

select a from foo where a >= 0 also.

1. ORDER:                0.74
2. A >= 0 with index:    0.73
3. A >= 0 without index: 0.56

Note that I used -B 16384 (very big pool) and run queries *twice* to get
all data into pool. What size of pool did you use? 64 (default) * 8192 =
512Kb,
but size of foo is 1.5Mb...

2. & 3. show that index slows data retrieval... as it should -:)
Also, does MySQL read table itself if it can get all required
columns from index?! I mean - did your query really read *both*
index and *table*? 
PostgreSQL has to read table anyway...

Vadim


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