Thread: [HACKERS] Is there any way to access heap_open() from _PG_init ??
Hello people,
I was trying to build an extension(Index related) on top of postgres.
During startup (_PG_init), I need to access some meta info of table/relation (like PK Column Position, FK Column Positions, Index Column Positions etc...) and load it into memory.
To accomplish that, In _PG_init() function, I tried to use the function heap_open() so that I can get the necessary table/relation info from that relation object, But I was not able to use, and the program is waiting in the heap_open() function indefinitely and postgres quits! Why am I not able to access?
Any workaround to access table relation object/Any way to get that info by some other means?
Thanks,
Sai Ram
Sai Ram
Sairam Gaddam <gaddamsairam@gmail.com> writes:
> During startup (_PG_init), I need to access some meta info of
> table/relation (like PK Column Position, FK Column Positions, Index Column
> Positions etc...) and load it into memory.
Why not fetch that info at first use, instead?
If you insist on doing it at _PG_init, you'll never be able to make the
extension work as a shared_preload_libraries item, where _PG_init
would be run in the postmaster. (I think local_preload_libraries would
be problematic too; not sure that you're inside a transaction there.)
You won't be able to retry after an error, or more generally to cope with
post-load-time changes in the data you want to cache.
It's probably possible to make it work as long as the library gets loaded
during a transaction, ie in response to some SQL command. Without seeing
your code we can't guess why its crashing though.
regards, tom lane