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Index performance on several milion records

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I have two tables :

Create table "million_data" (

Create Index "million_data_tst_key2" ON "million_data" ("MYTIMESTAMP","TABLE2_KEY")
Create Index "million_data_key2_tst" ON "million_data" ("TABLE2_KEY","MYTIMESTAMP") 

Create table "TABLE2" (
	"TABLE2_KEY" Number,
	"RECTITLE" Varchar2 (200),

The  table "million_data" has around  5000000000 records.

The TABLE2 has 10000 records only.

Counting the records number takes 500 seconds;

The question is how can I improve the performance of the SQL to get data joining the two tables ?

Which is the best approach to create the indexes on million_table? Is the composite index a good idea ? If I need to perform queries limiting the range of MYTIMESTAMP between two values, having an index on just the MYTAMESTAMP column leads to a better performance ?

Tnank you very much.

Best regrads

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Hi Jeff and welcome to the forum!

First, did you run autotrace to view the execution plan?


How many CPU’s do you have on your server?  Oracle parallel query is great for improving the speed of full-table scans:


Without indexes, Oracle will join the tables, but use a merge join.


This  is some of my notes on improving join speed:


For the whole story, check out my SQL tuning book:


Please reply and let me know if this helped.

Good luck!


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Hi Burleson,

Thank you very much for answering me.

As this Oracle software is installed on my client's server and I have not access to the machine itself I do not know how many cpu's it has, but I guess it might have four at least.

But I have still a question.

Imagine I have built a query which compares the mytimestamp column to a value, the composite index on mytimestap and table2key is enough for joining the tables or it would be better if the million_data table has two diferents indexes one on each column instead of of the composite index ?

I do not know how Oracle uses the table indexes.

Thank you very much.

Best regards

Jayme Jeffman

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Hi Jayme,

From sqlplus or sql developer, you can get what you need.

You. An see your cpu_count, it is in this view:

select * from v$parameter;

You can also use autotrace to reveal the execution plan.  Read the link I sent!

As to the composite index question, see here:


Good luck!

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