pgsql-server/doc/src/sgml/ref create_index.sgml

CVSROOT: /cvsroot
Module name: pgsql-server
Changes by: momjian@svr1.postgresql.org 04/04/19 22:00:27

Modified files:
doc/src/sgml/ref: create_index.sgml

Log message:

My question is whether postgres can index null values, and if not, do I
have to accept a full table scan when locating records.

It indexes them, but "is null" is not an indexable operator, so you
can't directly solve the above with a 3-column index. What you can do
instead is use a partial index, for instance

create index i on CUSTOMER.WCCustOrderStatusLog (WCOrderStatusID)
where Acknowledged is null and Processing is null;

That's a very nifty trick and exactly the sort of answer I was after!

Add CREATE INDEX doc mention of using partial indexes for IS NULL
indexing; idea from Tom.