Обсуждение: Given a view relation OID, how to construct a Query?
I'm doing some extension development (in C) and have a situation where I need to examine the target list of a view, but all I have is the view's oid.
An approach that works is (pseudocode):
SPI_connect();
"SELECT ev_action FROM pg_catalog.pg_rewrite WHERE rulename = '_RETURN' and ev_class=?oid";
Query *query = linitial(stringToNode(ev_action));
...
SPI_finish();
I backed into this by tracing through pg_getviewdef(). Is there a more direct way to do this without going through SPI?
I also looked at using postgres.c#pg_analyze_and_rewrite() against a query like "SELECT * FROM viewname" but the target list of the actual query wasn't what I was expecting (individual entry tags don't match those of the SPI approach above).
Thanks for your time!
eric
Eric Ridge <eebbrr@gmail.com> writes:
> I'm doing some extension development (in C) and have a situation where I
> need to examine the target list of a view, but all I have is the view's oid.
Open the relation and use get_view_query(), perhaps.
regards, tom lane
On Wed, Dec 9, 2015 at 4:04 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Eric Ridge <eebbrr@gmail.com> writes:
> I'm doing some extension development (in C) and have a situation where I
> need to examine the target list of a view, but all I have is the view's oid.
Open the relation and use get_view_query(), perhaps.
I figured there was something simple, but I couldn't find it. Thanks! Sadly, it's static.
eric
Eric Ridge <eebbrr@gmail.com> writes:
> On Wed, Dec 9, 2015 at 4:04 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Open the relation and use get_view_query(), perhaps.
> I figured there was something simple, but I couldn't find it. Thanks!
> Sadly, it's static.
FWIW, it's exposed in 9.4 and up. But in older branches you could
probably just copy it, it's not that big.
regards, tom lane
On Wed, Dec 9, 2015 at 5:07 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
FWIW, it's exposed in 9.4 and up. But in older branches you could
probably just copy it, it's not that big.
That's good to know, thanks. I did copy it and it's almost 3x faster than going through SPI. Thanks again for the pointer.
eric