Combining Hash Cluster And Indexes
Oct 28, 2010
A basic select and group by query I am optimising for my Database course has returned results that indicate it will perform better on a clustered index when returning a smaller number of rows (5% of the largest table) and on a hash clustered index when returning higher volumes (50% and 80%). I understand that it is possible to use more than one index type on a table to improve performance, but I am struggling to understand how I might establish a hash cluster and a cluster on the same table? and then use hints to drive the query down one access path or the other.
Site admin - this site is a very useful resource.
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Sep 10, 2012
RDBMS - 11.1.0.7, I it possible to convert indexes of a non-partitioned table to hash partitioned indexes by retaining table as non-partitioned?
If yes, is this what it is Creating a Hash-Partitioned Global Index - can be created for partitioned and non-partitioned tables?
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Jun 15, 2012
I had some query.
Actually had some table with following information
Here A,B,C are the vendors and Code is 21 and Amount is mentioned
Code Vendor Amount
21 A 56
21 A 62
21 B 31
21 C 100
21 C 100
Want to display top three vendor for that Code based on Vendor Amount
Code Vendor Amount
21 C 200(100+100)
21 A 118(56+62)
21 B 31
How should i do this?
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Jan 17, 2011
I'm having some trouble combining some data. I've done a lot of research into joins and merges, nothing really seemed to do what I needed. I could be over thinking it.
Basically, I want the query to look at the "info" table from a specified time-span (1 to 7). I want it to look at the source of the data and if it is "one_better" always use that data for that specific time. Otherwise, return the data from "one". The results don't care about the source of the data.
The "info" table I'm working with looks like this:
TIMEDATASOURCE
1DATA1one
1DATA1betterone_better
2DATA2one
3DATA3betterone_better
4DATA4one
4DATA4betterone_better
5DATA5 one
7DATA7one
I would like the results to look like this:
TIMEDATA
1DATA1better
2DATA2
3DATA3better
4DATA4better
5DATA5
7DATA7
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Aug 22, 2011
I have to implement a new logic such that , Old logic which pulls data will stay in place.now New logic pull data form SAP . So i have implemented the new logic in to the existing cursor as below.
i.e.
Cursor new_sap
old_query
Union
New_query;
I have 3 new cursor like dis. How to process these old and new cursors in FOR loop.. Ex:
For c1 in C2(order_number)
if order_source is sap then ( dis filters old data which is not in SAP)
new query in cursor should process
else
old query in cursor should process
end if;
How will i do this programatically.
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Aug 15, 2012
I have a table with 4 records with start_date and end_date fields
start_date end_date
1/1/2003 1/4/2005
1/1/2004 5/3/2006
1/1/2007 1/4/2008
1/1/2008 6/3/2009
as you see records 1,2 and records 3,4 have overlapping dates. I need to combine them to get continuous intervals. The result should be:
start_date end_date
1/1/2003 5/3/2006
1/1/2007 6/3/2009
Is it possible to do by SQL query?
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Apr 8, 2012
1. I Wnat to analyze the buffer cache hit ratio. This is what i did.
DECLARE
bufcac NUMBER(10, 2);
BEGIN
[Code]....
2. I would like to analyze the PGA and determine what percentage out of the maximum allocated PGA is being used. I tried the code below but can't find the percentage. Sad
SELECT NAME,
To_char(Decode(unit, 'bytes', VALUE / ( 1024 * 1024 ),
VALUE), '999,999,999.9') VALUE,
[Code]....
Apart from the little problem I have with number 2, not figuring out how to get the precentage seeing that all the data is store in the field VALUE.
I would also like to create a view that has both 1 and 2 in it, but whenever I try creating it, I got and error stating and INTO clause is expected.
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May 12, 2013
I have three select queries. Each of them returns a single column. I want the result of these queries into a single table..
I tried this way..
select * from
(first select),(second select),(third select);
this gives duplicate rows...
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Dec 11, 2012
Is there any way to combine an identifier and select statement in PL/SQL when using the insert into command?
e.g.
DECLARE
name := 'BOB';
BEGIN
insert into mytable(NAME, SLOWEST_LAP, FASTEST_LAP) name, (select min(time), max(time) from lLAP_TIMES);
END;
In the above statement I am trying to insert the identifier "name" (BOB) into MYTABLE.NAME, along with the result of the select query from the table LAP_TIMES ... min(time) into MYTABLE.SLOWEST_LAP, and, .... max(time) into MYTABLE.FASTEST_LAP.
If the above is possible in one statement how would I also combine an identifier, with two select statements into an "insert into" statement?
e.g.
name := 'BOB';
insert into mytable(NAME, SLOWEST_LAP, FASTEST_LAP, EVENT) name, (select min(time), max(time) from LAP_TIMES), (select race_event from MEET);
In the above example I am also trying to insert the result from MEET.RACE_EVENT into the column MYTABLE.EVENT
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May 31, 2013
Is there a way to prevent Apex from combining labels into an "other" category in the charts?
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Aug 21, 2012
I have a question.
When and Where HASH VALUE for a given SQL statement get generated?
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May 22, 2013
Is it true that the SQL hash is computed on the SQL text only ?
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Jul 12, 2012
what is Hash join?how it is different from inner join?what is the sign used for inner join?(eg: like the (+) sign used for outer join)?
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Jan 13, 2013
If i have a table T1 and a table T2. Table T1 is having 100 rows and table T2 is having 20 rows. When performing a Hash join ,which table should be used to make the hash table ,the larger one or the smaller one and why ?IF the data set is too small for considerations then please conser table T1 with 10 million of rows and table T2 with 1 million of rows.
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Nov 2, 2012
I see one of my SQL's which is ran by the user on a 10.2.0.3 database changing its SQL_ID after some runs even if the query is not changed a bit! However the HASH VALUE for this query remains the same.
how a same query can have different SQL_ID's but same HASH_VALUE?
Note: Statistics are not modified on the base tables of this query.
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Jun 27, 2010
I am facing a problem in fetching / updating records from a customer details table having around 20 million records. The table contains around 30 fields with 'MOBILE_NO' as primary key. most of the queries are having 'mobile_no' in where clause .I am planning to hash partition that table using mobile_no column as there is no other column available which can be used for partition.
clarify whether creating hash partition on such key would increase performance of data extraction as I have read on net that hash partitioning is not effective for performance tuning.
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Aug 7, 2013
I see that one of my queries from an application time is spending most of its time in the hash group by. I'm running Oracle 11g with a quarter rack exadata appliance. Is there a better way to run or design this table? query:
SELECT COUNT(*)
FROM (
SELECT "DDTMDAY", "MRKTNM", "BSMNM", "BSCNM", "CLNM", "CSCDNM", "BTSID", "SECTSEQID", "BNDID", "FAID", SUM("VATTCNT"), SUM("VMBLORGCNT"), SUM("VMBLTERCNT"), SUM("VSILENTRETRYCNT"), SUM("VCUSTBLKCNT"), SUM("VAXSFCNT"), SUM("VCEBLKCNT"), SUM("VWCDBLKCNT"), SUM("VT1BHLBLKCNT"), SUM("VPWRBLKCNT"), SUM("VNONBTSEQBLKCNT"), SUM("VSFULCALLCNT"), SUM("VDRPCALLCNT"),
[code]...
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Mar 16, 2011
What is the difference between Hash join and Nested Loops in pl / sql?
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Jun 12, 2012
I tried to search on google for "Hash Join" And "Sort Merge". But unfortunatly i am unable to understand that articles. "Hash join" And "Sort Merge".
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Mar 16, 2013
I created a single table hash cluster like this :
create tablespace mssm datafile 'c:appmssm01.dbf' size 100m
segment space management manual;
create cluster hash_cluster_4k
( id number(2) )
size 8192 single table hash is id hashkeys 4 tablespace mssm;
-- Created a table in cluster with row size such that only one record fits one block and inserted 5 records each with a distinct key value
CREATE TABLE hash_cluster_tab_8k
( id number(2) ,
txt1 char(2000),
txt2 char(2000),
txt3 char(2000)
)
CLUSTER hash_cluster_8k( id );
[code]....
If I issue the same query after creating unique index on hash_cluster_tab(id), the execution plan shows hash access and single I/O (cr = 1).Does it mean that to have single I/o in a single table hash cluster, we have to create unique index? Won't it create additional overhead of maintaining an index?
What is the second I/O needed for in case unique index is absent?
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Jul 18, 2012
I have a existing non partition table with more than 100 million records,planning to re design using Hash partition.This table doesn't has any range column to do range partitioning.
Table has 40 columns with a Primary Key on two columns (guest_sales_Id ,Version Flag). guest_sales_Id is unique for entire table but with anopther column version Flag declared as Primary key.(Version Falg will have only two distinct values in entire table)
If i do hash partition,do i need to declare on two columns which are declared ad Primary key ?If i use only guest_sales_id to declare hash prtition any issues ?
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Sep 27, 2010
I created the 32 hash partition on a fact table. Based on hash parititon technique it should evenly distribute data accross the different partition.But when i analyze the table and check the distribution its not at all even.
P_Name Tabspace num_Rows
SYS_P21TBS_TBS0
SYS_P22TBS_TBS0
SYS_P23TBS_TBS0
[Code]....
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Aug 29, 2013
I have to load data file into a table. And the requirement is as below:
Input Data:
1234|20130815|20130822|This is a test, this is the the part
3456|20130823|20130809|This is a test
3456|20130823|20130809|This is a test
3456|20130823|20130809|This is a test
3456|20130823|20130809|Siva 1234
The data should be inserted only in two rows as below:
When Value in first 3 fields is same, 4th field should be appended to the existing value in table.
1234|20130815|20130822|This is a test, this is the the part
3456|20130823|20130809|This is a testThis is a testThis is a testSiva 1234
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Mar 27, 2013
note we need to decrypt the data which is encrypted using dbms_crypto.hash algorithm. it is possible to decrypt dbms_crypt.hash
eg
SQL> select DBMS_CRYPTO.hash(utl_raw.cast_to_raw('Foo'), 3) FROM dual;
DBMS_CRYPTO.HASH(UTL_RAW.CAST_TO_RAW('FOO'),3)
--------------------------------------------------------------------------------
201A6B3053CC1422D2C3670B62616221D2290929
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Nov 18, 2010
Getting an ORA-00060 in our database. This is the alert log:
Wed Nov 10 08:01:54 2010
Global Enqueue Services Deadlock detected. More info in file
/opt/oracle/admin/ngboot/bdump/ngboot1_lmd0_13119.trc.
This is part of the lmd file:
oprocp : (nil)
opid : 0
group lock owner : (nil)
xid : 0000-0000-00000000
dd_time : 0.0 secs
dd_count : 0
timeout : 0.0 secs
[Code] ......
How do I find the SQL causing this? I have the hash value of 3180952482. should I open up en SR as this i logged in an lmd trace?
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Dec 27, 2012
With this table in local and remote database via a DBLink
CREATE TABLE PICTURES (
ID NUMBER(12),
PICNAME VARCHAR2(20),
PICTURE BLOB
);
How come I can get the hash of the picture column fine like this:
SELECT dbms_crypto.hash@dbLink(PICTURE, 3)from SCHEMA1.PICTURES@dbLink;
but I can't do it in a union with the local database?
SELECT dbms_crypto.hash@dbLink(PICTURE, 3)from SCHEMA1.PICTURES@dbLink
UNION
SELECT dbms_crypto.hash(PICTURE, 3)FROM SCHEMA1.PICTURES;
gives "ORA-06553: PLS-564: lob arguments are not permitted in calls to remote server"
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Mar 31, 2011
I was reading the documentation for oracle 11gr2, with reference to URL>.....
The following examples show how to correctly choose the cluster key and set the HASH IS, SIZE, and HASHKEYS parameters. For all examples, assume that the data block size is 2K and that on average, 1950 bytes of each block is available data space (block size minus overhead).Note that 34 hash keys are assigned for each data block
how they arrive at 34 hash keys because another portion of the document states
This space determines the maximum number of cluster or hash values stored in a data block. If SIZE is not a divisor of the data block size, then Oracle Database uses the next largest divisor.
if that is the case, then number of hash keys should be 1900/55 = 34.55 which should have rounded up to 35.
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Apr 12, 2013
At moment we use range-hash partitioning of a large dimension table (dimension model warehouse) table with 2 levels - range partitioned on columns only available at bottom level of hierarchy - date and issue_id.
Result is a partition with null value - assume would get a null partition in large fact table if was partitioned with reference to the large dimension.Large fact table similarly partitioned date range-hash local bitmap indexes
Suggested to use would get automatic partition-wise joins if used reference partitioningWould have thought would get that with range-hash on both dimension.
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Aug 5, 2010
I have to create a hash partition on fact tables.. we can use temp tablespace or permanent tablespace.
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Mar 13, 2012
While trying partition exchange feature of Oracle with 2 hash partitioned tables, I come to know that I can't directly exchange partitions between 2 partitioned tables
I have two hash partitioned tables , so to move partition data from one table to another will include-
1) Exchange from partitioned table to non-partitioned table.
2) exchange from non-partitioned table to new partitioned table.
But I am not sure in which hash partition my data will go in new partitioned table (data need to be moved has single key value on basis of which tables are partitioned),
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