Limited use of indexes in XE db?

I tried to use reverse key index in my XE database, but I cannot...
is this type of indexes disabled in XE db?
where can I found a list of all limitations in Express edition database?

how did you exactly use it, no problems here,
SQL> desc test;
Name                                      Null?    Type
FULLNAME                                           VARCHAR2(20)
ADDRESS                                            VARCHAR2(20)
SQL> create index test_ndx on test (fullname) reverse;
Index created.
SQL> create index test_ndx2 on test (fullname, address) reverse;
Index created.

Similar Messages

How to force the optimaizer to stop using an index ?

Hello,
I have an index on a very large table and I want to see how the applications running on this DB handles a situation in which this index does not exists.
Therfore I have 2 options:
1. drop the index - but this is too risky as if i will need to recreate it , it will last forever and will result in long application downtime which I can not afford.
The test and Dev environments does not contain ammounts of data like the prodicution so its hard to predict from these environments.
2. the second option is Modify the index columns statistics (which I have done) giving it low NDV (number of diftinct values) -- but sadly this did not work.
when cheking event 10053 I see a the line "Using prorated density: [ 1/(2*num_rows) ] of col #n as selectivity of out-of-range value pred" which I guess meens the High value of the column is lower then the value given it the query ( I do not run statistics every day , the current statistics for all columns (execpt this one ) suits best and I do not want to handle plan changes . also it will take a lot of time to gather table stats on daily basis.
So - to make a long story short - how do I force Oracle to avoid using an index but continue builing it and without dropping it?
I can not use the 'NO_INDEX' hint as it will requre change in many Applications.
I don need something like NO_INDEX hint on system level.
I am using Oracle 10g Enterprise edition.
the optimaized_mode is set to COST BASED.
Thanks in advance for any help resolving this complicated issue.
Regards,
Amit Zor.
ADBA.

user3698066 wrote:
Hello,
I have an index on a very large table and I want to see how the applications running on this DB handles a situation in which this index does not exists.
2. the second option is Modify the index columns statistics (which I have done)
I'm still wondering if there is a way of modifying the statistics of the index in such a way so that it is not used by the optimizer.
Since the main contributors of the formula for an simple b-tree index access path are the height of index, the number of leaf blocks and for the table access the clustering factor, may be you could come up with all those values bumped up to very large values for that particular index.
Unfortunately the only component of the formula that is not multiplied by a factor is the height of the index, which is sanity checked (at least in 10.2) when set manually and is limited to a (already quite unreasonable) 255, so you can't set it greater than 255, but the remaining attributes can be set more or less to whatever you want.
So you could come up with an manual modification of the index statistics like this. Note that I don't modify the NUM_ROWS and DISTINCT_KEYS values in an attempt to limit the risk of unwanted side effects of this modification.
begin dbms_stats.set_index_stats(
ownname=>'<index_owner>,
indname=>'<index_name>',
indlevel=>255,
numlblks=>1000000000,
clstfct=>1000000000,
avglblk=>1000000000/<num_distinct>,
avgdblk=>1000000000);
end;
/In a quick test I was successfully able to prevent a very selective index access path using these settings, but depending on your remaining statistics and the access paths chosen by the optimizer this might not work for you, at least not in all possible cases, e.g. an index unique scan won't cost more than 256 even using these settings because only a single leaf block by definition has to be visited in this case.
Of course I haven't checked thoroughly what other side effects this statistics fudging does have, so use at your own risk resp. test it in your non-production environment before even thinking about applying it to an production system.
Regards,
Randolf
Oracle related stuff blog:
http://oracle-randolf.blogspot.com/
SQLTools++ for Oracle (Open source Oracle GUI for Windows):
http://www.sqltools-plusplus.org:7676/
http://sourceforge.net/projects/sqlt-pp/

Can I refactor this query to use an index more efficiently?

I have a members table with fields such as id, last name, first name, address, join date, etc.
I have a unique index defined on (last_name, join_date, id).
This query will use the index for a range scan, no sort required since the index will be in order for that range ('Smith'):
SELECT members.*
        FROM members
        WHERE last_name = 'Smith'
        ORDER BY joindate, idIs there any way I can get something like the following to use the index (with no sort) as well:
SELECT members.*
        FROM members
        WHERE last_name like 'S%'
        ORDER BY joindate, idI understand the difficulty is probably; even if it does a range scan on every last name 'S%' (assuming it can?), they're not necessarily in order. Case in point:
Last_Name: JoinDate:
Smith          2/5/2010
Smuckers     1/10/2010An index range scan of 'S%' would return them in the above order, which is not ordered by joindate.
So is there any way I can refactor this (query or index) such that the index can be range scanned (using LIKE 'x%') and return rows in the correct order without performing a sort? Or is that simply not possible?

xaeryan wrote:
I have a members table with fields such as id, last name, first name, address, join date, etc.
I have a unique index defined on (last_name, join_date, id).
This query will use the index for a range scan, no sort required since the index will be in order for that range ('Smith'):
SELECT members.*
FROM members
WHERE last_name = 'Smith'
ORDER BY joindate, idIs there any way I can get something like the following to use the index (with no sort) as well:
SELECT members.*
FROM members
WHERE last_name like 'S%'
ORDER BY joindate, idI understand the difficulty is probably; even if it does a range scan on every last name 'S%' (assuming it can?), they're not necessarily in order. Case in point:
Last_Name: JoinDate:
Smith          2/5/2010
Smuckers     1/10/2010An index range scan of 'S%' would return them in the above order, which is not ordered by joindate.
So is there any way I can refactor this (query or index) such that the index can be range scanned (using LIKE 'x%') and return rows in the correct order without performing a sort? Or is that simply not possible?Come on. Index column order does matter. "LIKE 'x%'" actually is full table scan. The db engine accesses contiguous index entries and then uses the ROWID values in the index to retrieve the table rows.

How to use cfloop index value as part of another variable

Hello,
I have a RATE form that first asks "how many rates will you
be adding?" that answer generates a series of form elements based
on the answer. You then have a form grid to populate, 3 values for
each rate (price, code, name).
This part works fine. The issue is now I need to INSERT the
values into the table, so I need to use the INDEX value of the
cfloop to recreate the amount (and names) of the fields in the
INSERT statement. How do I escape, or re-create the evaluated form
elements ( in which their count is #i# as the loop goes) when I
need to evaluate for #i# AND evaluate for #form.sku_i_name# at the
same pass?
I am passing, for example, #form.sku_2_Name# where that might
equal "Half Page". The number 2 in that variable was assigned
during the form creation by the current index of a cfloop. Since my
action (insert) page does not know how many (out of 50 possible)
sku's are coming, how do I use the skuCount (another hidden value
passed as well) to create a proper INSERT SQL command when I need
to eval the form element and the index at the same time?
Obviously #sku_#i#_Name# does not work, and #sku_i_Name# does
not either... I know this can be done, and that I am just doing it
wrong.
Thanks for any help!

bigbrain28 wrote:
> Thank You, cfsearching! I don't quite understand 100%
how it works
As all three of us indicated you use array notation for this
type of
requirement. In ColdFusion you can use array notation or dot
notation
to access structure data. Almost all data in ColdFusion is
now some
type of structure.
I.E. #Form['myField']# is the same as #Form.myField#.
The advantage is that with array notation you can do things
you can not
do with dot notation. You can reference elements that have
keys that
are illegal variable names such as one with a space.
I.E. #url['my field'] is allowed, #url.my field# would fail
or course.
And you can concatenate the key string as we did with your
example.
I.E. #Form['aString' & aVariable]#
There are many powerful things one can do with this
knowledge. One can
access record sets with array notations. This can allow for
very
sophisticated parsing of a record set.
I.E. #myQuery['column'][row]#
You can dynamical call a variable. Thus creating dynamic code
that does
not even need to know what variables exist until run time.
I.E. #variables[anyName]#
This just scratches the surface.

Why cant we use sy-index in loop and endloop?where exactly we used sy-index

hi
can u help me for this

Hi...
Genereally Sy-index is used in iterative cases like
while....endwhile
and
Do.... Enddo
In LOOP ..... Endloop.... We should use SY-TABIX....
It would be more consistent we use sy-tabix as we loop at internal table so this SY-TABIX points to the current record its reading...
we can use sy-index but rarely depends on condition.....
SY-INDEX and SY-TABIX will not be same always in LOOP and ENDLOOP
Rewards points if satisfied..
Regards
Narin Nandivada

Use of index based on an attribute when doing an order by

Hi,
I create a table and its indexes like this:
create table poc_wip2 of xmltype
xmlschema "http://www.derwent.co.uk/wpi.xsd" element "WPI"
alter table poc_wip2
add constraint poc_wip2_pk primary key
(XMLDATA."BibPt"."PDOC_COUNTRY",
XMLDATA."BibPt".pdoc_serial, XMLDATA."BibPt".pdoc_kind)
create index pan_index on poc_wip2 t
(extractvalue(value(t),'/WPI/BibPt/@pan'))
Now when I run the query:
select extractvalue(value(t),'/WPI/BibPt/@pan')
from poc_wip2 t
order by extractvalue(value(t),'/WPI/BibPt/@pan')
I can see that a full table scan occurs. I cannot get the query to use the index built on the pan attribute.
I tried adding a INDEX_FFS hint, but this does not work when I name the pan_index, it only works with
INDEX_FFS(t), in which case the query then uses the primary key index.
Is it possible to get the query to use the pan_index index?
Thanks
Pete

Hi
Create a restricted key figure with the ZSE_BPNV1 and mention the values of the attribute and display the values
Here you can mention your charecteristic and attrribute value both with the key figure
Assign points if useful
Regards
N Ganesh

Use of Index, Histograms, etc

Hi all,
We're using Oracle 9.2.04.
I have a table with 500000 rows.
So I have a query that returns only 30242 for a month, like:
SELECT * FROM T1
WHERE TO_CHAR(DT, 'MM/YYYY') = TO_CHAR(ADD_MONTHS(SYSDATE, -1), 'MM/YYYY')
I have a index for this column:
CREATE INDEX IND_T1_DT_FMT ON T1 (TO_CHAR(DT, 'MM/YYYY'))
TABLESPACE TBS_SOME_USER;
There are statistics for this table.
Looking the table data, I have the following distribution:
Qty     MON/YY %
1         Feb-09     0.000219142
99         Apr-09     0.021695016
38439     May-09     8.42358314
98231     Jun-09     21.52649641
1         Jul-06     0.000219142
139959     Jul-09     30.6708362
1         Aug-02     0.000219142
1         Aug-07     0.000219142
141362     Aug-09     30.97829184
30242     Sep-09      6.62727962
7990              1.750941213But when a perform the query (that returns 30242 rows - 6.63% of table):
SELECT * FROM T1
WHERE TO_CHAR(DT, 'MM/YYYY') = TO_CHAR(ADD_MONTHS(SYSDATE, -1), 'MM/YYYY')
Oracle uses FTS:
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=432 Card=45633 Bytes
=3011778)
1 0 TABLE ACCESS (FULL) OF 'T1' (Cost=432 Card=45633 Bytes
=3011778)
So, Oracle should not use the index in this case?
Is there any way to gather statistics for this table with a index based function?
Something like this:
EXECUTE DBMS_STATS.GATHER_TABLE_STATS(ownname => 'U1',
tabname => 'T1', method_opt => 'FOR COLUMNS TO_CHAR(DT, ''MM/YYYY'')',
cascade => true, degree => 4);
How can I create histograms for this case?
Or other solution, like Partition?
thank you very much!!!!

Always treat dates like dates.
This
SELECT * FROM T1
WHERE TO_CHAR(DT, 'MM/YYYY') = TO_CHAR(ADD_MONTHS(SYSDATE, -1), 'MM/YYYY')Should be more like this:
SELECT * FROM T1
WHERE DT BETWEEN TRUNC(ADD_MONTHS(SYSDATE,-1),'MM') AND TRUNC(SYSDATE,'MM')-1 ;Then you should index DT.
But, should this query use the index?
Touch and go at 6.63%.
Give it a go using dates as dates and see if it makes a difference.
Is there a problem with the performance of the FTS?

Use of Index although a great number of rows is returned....

Hi ,
I have created the following table:
create table all_obj select * from all_objects;
Then i created some indexes:
create index idx_obj on all_obj (object_name)
create index idx_owner on all_obj (owner)
Then i issued the sql statement:
SQL> select count(object_name),owner from all_obj group by owner;
COUNT(OBJECT_NAME) OWNER
               719 MDSYS
               266 SCOTT_BI
               266 INFO_BI
                 2 TSMSYS
               118 DMSYS
20146 PUBLIC
                 6 OUTLN
               171 CTXSYS
               612 OLAPSYS
               400 SYSTEM
               168 EXFSYS
43 SCOTT
                32 DBSNMP
              1638 ORDSYS
                 5 ORDPLUGINS
               866 SYSMAN
               284 XDB
20993 SYS
               264 INFORMATICS
               212 WMSYS
COUNT(OBJECT_NAME) OWNER
                 8 SI_INFORMTN_SCHEMA
21 rows selectedand...:
SQL> analyze table all_obj compute statistics;
Table analyzedAt last , i issued the following pair of sql statements:
SQL> select object_name,owner from scott.all_obj where owner='SCOTT'
2 /
43 ãñáììÝò åðéëÝ÷èçêáí.
Ðñüãñáììá åêôÝëåóçò
Plan hash value: 2272571446
| Id | Operation                   | Name      | Rows | Bytes | Cost (%CPU)| T
ime     |
|   0 | SELECT STATEMENT            |           | 2249 | 65221 |    68   (0)| 0
0:00:01 |
|   1 | TABLE ACCESS BY INDEX ROWID| ALL_OBJ   | 2249 | 65221 |    68   (0)| 0
0:00:01 |
|* 2 |   INDEX RANGE SCAN          | IDX_OWNER | 2249 |       |     6   (0)| 0
0:00:01 |
Predicate Information (identified by operation id):
   2 - access("OWNER"='SCOTT')
ÓôáôéóôéêÜ
          0 recursive calls
          0 db block gets
         12 consistent gets
          0 physical reads
          0 redo size
       1692 bytes sent via SQL*Net to client
        407 bytes received via SQL*Net from client
          4 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
         43 rows processedand
SQL> select object_name,owner from scott.all_obj where owner='SYS';
20993 ãñáììÝò åðéëÝ÷èçêáí.
Ðñüãñáììá åêôÝëåóçò
Plan hash value: 2272571446
| Id | Operation                   | Name      | Rows | Bytes | Cost (%CPU)| T
ime     |
|   0 | SELECT STATEMENT            |           | 2249 | 65221 |    68   (0)| 0
0:00:01 |
|   1 | TABLE ACCESS BY INDEX ROWID| ALL_OBJ   | 2249 | 65221 |    68   (0)| 0
0:00:01 |
|* 2 |   INDEX RANGE SCAN          | IDX_OWNER | 2249 |       |     6   (0)| 0
0:00:01 |
Predicate Information (identified by operation id):
   2 - access("OWNER"='SYS')
ÓôáôéóôéêÜ
          0 recursive calls
          0 db block gets
       3345 consistent gets
          0 physical reads
          0 redo size
     801069 bytes sent via SQL*Net to client
      15774 bytes received via SQL*Net from client
       1401 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
      20993 rows processed
The question is: why the second query uses the index since a great number of records is returned......????
I use Oracle10g.v.2
Thanks...
Sim

You were right.....
using:
SQL> EXEC DBMS_STATS.gather_schema_stats(ownname => 'SCOTT');
the optimizer does follow the 'waited' access path....for the 'PUBLIC' records.....
It seems that using the analyze table statement does not permit to gather all the necessary statistics.....(that's why it is depreciated)...!!!!
Thanks.....
Sim

Restrict the use of index while quering

Hi All
I have a simple emp table with columns empid, name, sal. Empid has a primary key imposed.
Now when i write a statement like this,
select * from emp where empid = <value>;
the optimizer will make use of index.
The question is........... is there anyway to make oracle bypass the use of index without change in above query.

Why do you worry of performance issues when the table size is small , when it is huge and the column you r trying use in the query is also indexed the oracle finds the Best execution method to do the execution whether index exists or not , Oracle has a very intelligent Optimizer and no need to use hints unless and until it is really mandatory or when u r using a very complex query where Oracle is not able to deduce the best Execution plan . But by all means you should look at the execution plan how a cerain query Oracle knows of doing it or when u have a diferering opinion then only at that point you force a Optomizer Hint . For other normal cases like the one you are asking it is best to get the results how Oracle executes it and no forcing is required .

What is use of index by binaary_integer

Hi All,
I have created to program of collection where we use index by binaary_integer in one program and not use index by binaary_integer in second program, but result is same, any body help me what is use of index by binaary_integer here
1- Declare
Type emp_table_type is table of
emp%rowtype index by binary_integer;
my_emp_table emp_table_type;
Begin
select * bulk collect into my_emp_table from emp;
for i in my_emp_table.first..my_emp_table.last
loop
dbms_output.put_line(my_emp_table(i).ename);
end loop;
end;
2- Declare
Type emp_table_type is table of
emp%rowtype;
my_emp_table emp_table_type;
Begin
select * bulk collect into my_emp_table from emp;
for i in my_emp_table.first..my_emp_table.last
loop
dbms_output.put_line(my_emp_table(i).ename);
end loop;
end;
your suggestion would be greatly appreciated.

here is one for you.
http://download.oracle.com/docs/cd/E11882_01/appdev.112/e17126/composites.htm#CHDEIDIC

Amount of temporary tablespace size used for index rebuild

Hi All,
I want to know approximate amount of temporary tablespace size used for index rebuild. I need this information to avoid the insufficient temporary tablespace error during the huge index rebuild.
Is there a query or procedure to find it out.
Thank you.

Hi,
While creating the index, the temporary segment is created in the permanent tablespace. So permanent tablespace must have sufficient space.
http://www.oracle-base.com/articles/10g/SpaceObjectTransactionManagement10g.php
http://aprakash.wordpress.com/2010/01/05/numeric-segment-name/
Anand

How to use the index method for pathpoints object in illustrator through javascripts

hii...
am using Illustrator CS2 using javascripts...
how to use the index method for pathpoints object in illustrator through javascripts..

Hi, what are you trying to do with path points?
CarlosCanto

How do I use the Index Values property node with a multidimensional array.

I am using a 2D array to store operator inputs on my front panel. I only want to display one element to the operator at a time. I am trying to use the Index Values property node to change the displayed element. However, I can only get the Rows index to work. How do I direct the Columns index as well? The help says to use one per dimension. I need clarification on what this is talking about. I've tried adding a second element to the property node, 2 seperate property nodes, and diferent wiring techniques. (series, parallel)

If you only wire up one of the inputs (col or row) what you get out is a 1D array of either the column or row. If you wire controls to both, then you will get one element out of the array. Getting a single element in a 2D array requires you to specify both a row and column.
Message Edited by Dennis Knutson on 02-08-2007 08:34 AM
Attachments:
Index 2D Array.PNG ‏2 KB

Use of substr function will avoid the use of indexes in a table

i have one table which will contain some 3,00,000 records, it contains some 11 primary keys i am using some update statements to update some fields in the records (of 3,00,000 i will compare some 1,50,000 records with 1,50,000 another records) i am using substr function in all the select statements. whether usage of substr function will avoid the use of index
can any one clarify?

contains some 11 primary keys by this I suppose you mean to say the table has a composite PK on 11 columns.
i am using substr function in all the select statementsCould you please post your SQL statement?

Use of Indexes in select query

Hello,
This is on a 9i install.
There is an index called form_id_idx on the form_id column.
Why does this query use the index (autotrace indicates range scan on the index):
select count(*) from table_name where form_id=123456;
but this query does NOT use the index (autotrace indicates full table scan):
select accepted from table_name where form_id=123456;
This second query runs much faster when I use a hint on the index. Any help/suggestions?
Thanks.

The first query does NOT have to go to the Table it all. It can read the index to count the number of rows for "form_id=123456". An Index Range Scan would be fast.
The second query has to go to the table to get the values for the "accepted" column for all the rows that have "form_id=123456". Remember that every get can require a read of 2 or more blocks -- at least one, probably 2 or 3, from the index and 1 from the table. If the number of rows is likely to be large then the number of block get operations would be high. In such cases, Oracle computes that it is faster to do a small set of multiblock reads to read the whole table (Table FullScan).
Therefore, the optimzer weighs :
a. how many rows it thinks will satisfy "form_id=123456"
b. how many index + table block gets it would have to execute (all as single block read calls to the OS)
versus
x. how many multiblock read calls it thinks it has to execute to read the whole table
If the available statistics on number of rows, cardinality or density and the size of the table indicate that operation "x" would be cheaper then operations "a" + "b", Oracle would prefer the latter.
Hemant K Chitale
http://hemantoracledba.blogspot.com

Limited use of indexes in XE db?

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