Thanks for the explanation.
On Mon, May 6, 2013 at 8:43 PM, Jasen Betts <ja...@xnet.co.nz> wrote: > On 2013-05-06, Tim Uckun <timuc...@gmail.com> wrote: > > --047d7b2e4ea07402b004dc034a3b > > Content-Type: text/plain; charset=UTF-8 > > > > Say I have a select like this. > > > > SELECT * FROM table where field = X OR field = Y limit 1 > > > > And I have two records one that matches X and one that matches Y will I > > always get X because the evaluation will stop after the first clause in > the > > OR matches? > > no. there is no guarantee which matching row you will get. Testing may > suggest that one answer is preferred but udating the table can change > which one. also you may get a different row without updating the table. > > > What about for IN (X, Y) > > same deal. > > > how about if I am doing an update > > > > UPDATE table1 set x=table2.y where table1.field1 = table2.field1 OR > > table1.field2=table2.field2 > > > > Will it update based on field1 if both fields match? > > what difference does that make to the result? > > > Basically I want to know if and how OR shortcuts the evaluation. > > In a word. "unpredictably". > > The planner will try to do the cheapest, most useful side first. > > -- > ⚂⚃ 100% natural > > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
