On 07/23/2013 11:24 AM, Craig Ringer wrote: > On 07/21/2013 10:42 PM, Миша Тюрин wrote: >> >> hi, list, again. the next proposal into auto explain. one would be happy if >> could set list of target tables and indexes. sometimes it is very hard to >> detect who is using your indexes. but turn total logging on under thousands >> transactions per seconds is not seems like nice idea couse size of resulting >> log files (cpu utilization might not be so critical) > > That sounds like a good idea - and since auto_explain is a contrib > module, it could potentially be a way to get into PostgreSQL > development. The code is in contrib/auto_explain/auto_explain.c . > > The challenge here is that planned queries don't just touch one table or > index. You'd need to walk the query plan (a graph of Node structures) to > determine which table(s) and index(es) are touched by the query there's > something in the sources for it already (I haven't checked).
Showing that I'm still very much learning this area myself, a bit more looking around found: http://www.postgresql.org/docs/current/static/querytree.html which makes it clear that the range table for the query will contain what you want. I suspect you'll need to find CTEs and subqueries and extract the relations they touch; I haven't yet checked to see whether they're aggregated into the top level range table, but suspect not. You'll find the code in src/backend/nodes/print.c informative and useful, though not directly reusable. Reading src/include/nodes/primnodes.h would be a good idea; it shows how subqueries, etc, are represented. -- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
