Knut Anders Hatlen wrote:
Rick Hillegas <[email protected]> writes:
Hi Brian,
In a previous response Peter Ondruška noted that you could use bulk
import to speed up your inserts if your source data lived in a
properly formatted file.
Even if your source data does not live in a file, you can still get
bulk import speed (and the benefits of your generated key) by using
table functions--provided that you upgrade to 10.4. If you wrap your
source data in a table function, then you can bulk insert your data as
follows:
insert into MY_TABLE( NON_GEN_COL1, ... NON_GEN_COL_N )
select * from table( MY_TABLE_FUNCTION() ) s
The internal SQL syntax allows you to add an optimizer override here
(--DERBY-PROPERTIES insertMode=bulkInsert) which I think speeds it up
even more, though I'm not sure exactly what it buys you. This override
is used in the import code and in the SYSCS_UTIL.SYSCS_BULK_INSERT
system procedure, but you're not allowed to use it in your own SQL
queries, it seems. The (undocumented) SYSCS_BULK_INSERT procedure does
exactly what Rick's example does, except that it also adds the optimizer
override.
The procedure only works on old-style table functions, though. Does
anyone know what performance gains one can expect by using
SYSCS_BULK_INSERT instead of INSERT INTO ... SELECT FROM? Would it be
worth the effort to create a similar mechanism for the new-style table
functions?
Hi Knut,
It appears to me that this setting (insertMode=bulkInsert) is inspected
when binding an INSERT statement. If the bind() logic finds this
setting, then it escalates the lock mode for the target table to be a
table level lock. Other than that, I cannot find any other use of this
setting. Comments around this code, however, indicate that there might
once have been other implications and that this setting, which is now
unconditionally accepted, used to be silently rejected in certain
situations, including insertion into a synchronized client database,
insertion into a table which has triggers, and deferred mode insertion
(see the comments on InsertNode.verifyBulkInsert).
It appears to me that the benefit now conferred by this setting can be
achieved by setting the lock mode on the table to be table level. So you
would preface the INSERT statement above with the following statement:
lock MY_TABLE in exclusive mode
That, at least, is what I have gleaned from a code inspection.
Regards,
-Rick
