Oracle 12C In-memory : Part 3 (IMCU pruning)

For other parts : Part1 , Part2

Let’s see a quick example of in-memory pruning using storage index :

In-memory white paper : “A further reduction in the amount of data accessed is possible due to the In-Memory Storage Indexes that are automatically created and maintained on each of the columns in the IM column store. Storage Indexes allow data pruning to occur based on the filter predicates supplied in a SQL statement.An In -Memory Storage Index keeps track of minimum and maximum values for each column in an IMCU.When a query specifies a WHERE clause predicate, the In-Memory Storage Index on the referenced column is examined to determine if any entries with the specified column value exist in each IMCU by comparing the specified value(s) to the minimum and maximum values maintained in the Storage Index. If the column value is outside the minimum and maximum range for an IMCU, the scan of that IMCU is avoided”

Quick example :
Continue reading

ORACLE 12C in-memory : Part 2 (Read consistency)

This is the second blog post about the new in-memory feature of oracle database 12c.For the preceding post Part 1

UPDATE 10/11/2014 : Flushing the buffer cache before testing to check for physical reads

In this post i will try to demonstrate how read consistency is maintained in the in-memory column store and determine how much work is done on behalf. Please read the white paper about in-memory before (you can find a link in the bottom of the page).

Let’s begin by creating our testing table and loading it on the in-memory column store :
Continue reading