Hello!

Using DBISAM v4.23.

We have a process that regularly performs big mods on a set of large tables:

 -alter table
 -reindex
 -full text index


What can we do to make these processes really rip?


a) Does Exclusive make any of the above faster?  (Which operations, are faster, specifically?)

b) Does it help to drop all indexes before an ALTER TABLE? (the alter table does not
affect indexed fields)

c) What can we do to make any of the above as fast as possible?

Thanks!

Sam,

<< a) Does Exclusive make any of the above faster?  (Which operations, are
faster, specifically?) >>

These operations already operate with exclusive access to the table.

<< b) Does it help to drop all indexes before an ALTER TABLE? (the alter
table does not affect indexed fields) >>

No, that won't make any difference.

<< c) What can we do to make any of the above as fast as possible? >>

There really isn't much you can do besides possibly bumping up the memory
buffering:

http://www.elevatesoft.com/dbisam4d7_customizing_engine.htm

under "Memory Buffer Customizations".

These types of operations are primarily disk-bound, so the bumping up the
memory buffering may not help that much overall.

For better full-text index performance, however, you should update to the
latest 4.25 build:

http://www.elevatesoft.com/scripts/incident.dll?action=viewrep&category=dbisam&release=4.25&type=f&incident=2446

--
Tim Young
Elevate Software
www.elevatesoft.com

Tim,

>For better full-text index performance, however, you should update to the
>latest 4.25 build:

We upgraded from v4.25 b6 to v4.25 b7 and the re-indexing of the full-text search index on
700MB database dropped from 1 min 18 sec to less then 1 sec. What was that? Is that
expected? Does the full text index actually getting rebuild in b7?

This is an SQL that we used to reindex

alter table address TEXT INDEX (Address1, Address2, City, PostalCode, FirstName, LastName,
Company, Phone, EMail)

Full text search appears to be working anyway... Could be using the old index though.

We did few tests around ALTER TABLE TEXT INDEX command

It appears that if list of the fields is exactly the same as it was before - the command
does not do anything.

Questions:

- Is that by design in 4.25 b7 ?
- How can we force index rebuild ?
- How can we drop TEXT INDEX completely?

Alex,

<< - Is that by design in 4.25 b7 ? >>

It has always been that way.

<< - How can we force index rebuild ? >>

Alter the table and drop the text index by setting the text index fields to
blank, or repair the table.

<< - How can we drop TEXT INDEX completely? >>

ALTER TABLE MyTable
TEXT INDEX ();

--
Tim Young
Elevate Software
www.elevatesoft.com