How the database fills in IM expressions (IM 5.4)

Upper connection IM 5.3. This chapter is IM Chapter 5 of the series Use In-Memory Expression optimization query part IV how to fill in the database IM expression .

How to fill the database IM expression

In the memory coordinator process （IMCO） Under the guidance of , Space management work process （Wnnn） Will automatically IM The expression is loaded into IMEU in .

The database will add each compression unit in memory （IMCU） Fill or repopulate tasks , It contains the user-defined or... To be populated IM Information about which virtual columns of the expression . Depending on INMEMORY_EXPRESSION_USAGE and INMEMORY_VIRTUAL_COLUMNS Initialization parameter settings .

Be careful ：

DBMS_INMEMORY.IME_CAPTURE_EXPRESSIONS The process will automatically add the detected expression as a hidden virtual column .

Wnnn Process creation IMCU. Need to create IMEU, The process will perform the following additional steps ：

1. Create an expression value

2. Convert values to columnar format , And compress it into memory expression units （IMEU）

3. Each one IMEU Link to its associated IMCU

Be careful ：

With IMEU Increase in the number of expressions stored in , The work process may consume more CPU To evaluate the expression value . This overhead may increase the fill time .

To be continued .

Here are IM Content of series articles ：

In-Memory The manual : Preface （IM- Preface ）

Chapter one Oracle Database In-Memory Relevant concepts (IM-1.1)

Chapter one Oracle Database In-Memory Relevant concepts （ To continue ）(IM-1.2)

Chapter two Oracle Database In-Memory Architecture ( On ) (IM-2.1)

Chapter two In-Memory Architecture (IM-2.2)

Chapter two IM Architecture ：CPU framework ：SIMD Vector processing （IM-2.3）

The third chapter Enable and adjust IM The size of the column store （IM-3.1）

Chapter four by In-Memory Enable fill objects （IM-4.1 The first part ）

Chapter four by In-Memory Enable fill objects （IM-4.2 The second part ）

Chapter four by IM Enable and disable columns for fill objects （IM-4.3 The third part ）

Chapter four by IM Enables the placement of fill objects NO INMEMORY The table specifies INMEMORY Column properties ： Example （IM-4.4 The fourth part ）

Chapter four by IM Enable and disable tablespaces for padding objects IM Column store （IM 4.5）

Chapter four Enable and disable... For materialized views IM Column store （IM 4.6）

Chapter four by IM Enables forced filling of filled objects In-Memory object ： course （IM 4.7）

Chapter four by IM Enable fill objects to IM Column storage enabled ADO（IM 4.8）

The fifth chapter Use In-Memory Expression optimization query （IM 5.1）

IM The purpose of the expression （IM 5.2）

IM How expressions work （5.3）

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