Hello Hackers,
I work on a foreign data wrapper for a legacy system. I generally find the hook system very useful and flexible way to
extendPostgres.
The post parse analyze hook almost fits what I need, but I have a few use cases where I would need to tap right into
theparsed queries but before any catalog based validation is done.
Please find the attached trivial patch for this new hook.
One of the use cases I have is this:
I have table like data structures in the source system for the FDW I work on.
These tables are sometimes too big and the source system is able to filter and join them with limitations, thus it is
notoptimal to transfer the data to Postgres.
At the same time I want the users to think in terms of the original tables.
The idea is to rewrite the SQL queries like this:
“SELECT * FROM tableA a, tableB b WHERE a.id=b.id AND a.col1=1234 AND b.col2=987”
to:
“SELECT * FROM fdw_tableA_tableB ab WHERE ab.col1=1234 AND ab.col2=987”
This rewritten query would be handled by the FDW table that I previously added to the catalog.
The reason I want this new hook is that I don’t want tableA and tableB to be in the catalog.
Looking forward to hear your thoughts, opinions, comments.
Best regards, David