GG with sql

Question

Hi,
I'm using GG with filter command, I would like to know the internal process of filter, If I'm using filter or SQLexec COMMAND IN EXTRACT , Whether that particular filter condition is executer against database table or its run against log file itself?
also is it possible to manipulate the data in redolog file itselfe, if not , whether the paricular filter condition will run every for commit. in this case always the command run against db, could you plz clarify how the filter or sqlexec, or sqlprdicat run in inside of the database,????
is there any performance issue will occur?
Thanks in Advance,
Annamalai

Answer 1

Annamalai,
This appears to be a double post so I'll only answer your new questions here.
The SQLEXEC query is executed in the database; there is no method (that I know of) to query the transaction logs but OGG definitely doesn't do it. We simply read it chunks and parse the LCRs.
FILTER's simpler cousin, WHERE, sometimes confuses first timers because it is not a database where clause but simply a conditional filtering construct against the change data.
There is no "sqlprdicat" but if you were trying to save a second with shorthand it cost me 10 seconds to look it up to make sure. Please do not shorten words especially when related to syntax and parameters.
SQLPREDICATE is used during initial loads, which essentially issue a select * and convert the results into insert statements, but it allows you to add a database where to the select * query.
To answer your final question, yes, anytime replication stops to issue a database query via SQLEXEC it will be slower than not stopping and issuing a query. You can run two extracts side by side, one with the SQLEXEC and one with no SQLEXEC to determine the delta on your particular systems.
Have fun,
-joe