Submitted by: Gareth Marshall (garethm)

Attachments:
TEST.zip

I am using Firebird 2.5.2 Security Update 1 build 26540, 64-bit on Windows 7 64-bit. I am testing using application developed with Delphi XE2 Update 4 Hotfix 1 and IBObjects 5.2.0 Build 6. I am running my tests on Windows 7 SP1 64-bit. The same database file is used for all tests.

The database is using the UTF8 character set, and a page size of 8192 bytes. The connections are done using the UTF8 character set. The database contains just a single table with the following schema:

CREATE TABLE TEST ( NAME varchar(50) );

The table contains no data.

I generate a query that includes a number of tests ORed to each other. Each test just checks to see if the NAME field is equal to the string form of a number one larger that the one before, producing n terms in the WHERE clause.

For example, if n is 5, the following query is used:

SELECT * FROM Test T WHERE
http://T.Name = '1'
OR http://T.Name = '2'
OR http://T.Name = '3'
OR http://T.Name = '4'
OR http://T.Name = '5'

When run against classic server, I can have at most 3173 terms in the WHERE clause before the query string itself reaches a length of 65530 characters and then returns an error. This is pretty much expected behaviour.

When run using the embedded engine, I can successfully have 1052 terms in the WHERE clause. In my tests, 1053, 1054, and 1056 terms in the WHERE clause cause Firebird to hang when attempting to prepare the query (1052 terms would prepare in less than a second; after 30 seconds I killed the test for these values). Testing with 1088 or more terms causes the test application to crash with a stack overflow in the fbembed.dll. 1052 terms has a query string of length 20989 characters, while 1053 terms has a query string of length 21010.

I have not tested any other configurations.