Theres a script on metalink - part of trcanalzye (Carlos S?) I think.
Anyway, there's a coe_xfr_sql_profile.sql script that will dump a profile
for a sq_lid to a SQL script.
In that profile script it creats you'll, see INDEX_FS or INDEX_FFS for the
index you're interested in.
You can change that line to INDEX_RS and run the script to create the
profile and force a range scan and that line in the plan. Then test your
performance and verify that the profile is used and that you get the range
scan.
Chris
On Sat, Aug 11, 2018, 4:34 PM <niall.litchfield@xxxxxxxxx> wrote:
I suggest that you modify the code that creates the table on the fly to.
1. Create the table as currently
2..SET statistics on the table that tell the optimizer it's got lots of
rows in it (and is quite large and .. and) same for the index. Then
schedule a gather later.
On Fri, 10 Aug 2018, 14:51 Chris Stephens, <cstephens16@xxxxxxxxx> wrote:
Is there a way to tell Oracle to use an index range scan instead of an
index full scan?
We have a table that gets created on the fly and quickly accumulates
100's of millions of rows before statistics are collected. Never mind why
the table has no statistics (it's a (longish) story). As the table
accumulates data, another process hits it with a piece of SQL that has a
variable number of predicates of the from "id between :id1 and :id2 OR id
between :id2 and id3 OR...". We have an index to support that SQL. Oracle
initially chooses to full scan that index instead of range scan it until
statistics are collected. Full scan performance is unacceptable. Is there
a way to force the index range scan version? We can't use baselines
(another story).
We've tried INDEX_RS and INDEX_RS_ASC after observing INDEX hint doesn't
get us what we want since index is already being used. INDEX_RS and
INDEX_RS_ASC aren't in official documentation so I'm not even sure they are
valid hints.
As I write this, it occurs to me that dynamic sampling might help here
and will try that but that obviously comes with some overhead. Any other
options?
Thanks for any insight.
chris
