Title: col_usage$ question
Does anyone know what this table (sys.col_usage$) is used for? To me it sounds like something that CBO might appreciate ... but any ideas? It is referenced by dbms_stats and dbms_stats_internal packages ...
Thanks in advance
Raj
That is a new table in Oracle 9 and is used by Oracle to track what columns
are used in predicates. At present the only use of that information that I
am aware of is in the procedure dbms_stats.gather_table_stats ( ...,
method_opt => 'for columns ... size auto');
At 09:29 AM 11/18/2003, you wro
Raj:
Wolfgang is right. It is populated by SMON (I think every 15mins SMON
flushes the data to COL_USAGE) and the predicate columns are updated
(or collected) from the hard parse of the SQLs.
Best Regards,
K Gopalakrishnan
-Original Message-
Wolfgang Breitling
Sent: Tuesday, November
Thanks KG,
Raj
Rajendra dot Jamadagni at nospamespn dot com
All Views expressed in this email are strictly personal.
QOTD: Any clod can have facts, having an opinion is an art !
-Original Message-
Sent: Tues
Thanks Wolfgang.
Raj
Rajendra dot Jamadagni at nospamespn dot com
All Views expressed in this email are strictly personal.
QOTD: Any clod can have facts, having an opinion is an art !
-Original Message-
Sent
Title: col_usage$ question
Hi!
If you describe this table then you see that this
table stores column usage information in filter and join predicates for database
objects. From describe, you see there are several filter and join conditions
tracked for an object's (obj#) columns (i
jendra
To: Multiple
recipients of list ORACLE-L
Sent: Tuesday, November 18, 2003 6:29
PM
Subject: col_usage$ question
Does anyone know what this table
(sys.col_usage$) is used for? To me it sounds like something that CBO might
appreciate ... but any ideas? It is referenced by dbms_stats and dbm
Absolutely
At 01:39 PM 11/18/2003, you wrote:
Could the column info be used to 'recommend' indexing?
Daniel Fink
Tanel Poder wrote:
Hi! If you describe this table then you see that this table stores column
usage information in filter and join predicates for database objects.
From describe, you
At 11:04 AM 11/18/2003, you wrote:
Hi!
If you describe this table then you see that this table stores column
usage information in filter and join predicates for database objects. From
describe, you see there are several filter and join conditions tracked for
an object's (obj#) columns (intcol#)
Bingo!
I did pretty much the same thing for an 8i DW with plenty of ad-hoc queries.
I had no way of knowing what those ad-hoc queries might look like, and they
will change over time. So I set up a polling process to do a textual parse
of v$sql for those SQLs with highest disk_reads and/or buffer_g
Title: col_usage$ question
Thanks Tanel,
I also found that whenever one issues
dbms_stats.flush_database_monitoring_info(), it updated some info in col_usage$
as well with mon_mods$ of course. That's where I found this reference and hence
my original email.
Thanks everyone.
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