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MySQL Internals Manual


23.18.19 position

Purpose

Provide the MySQL server with position/offset information for last-read row.

Synopsis

virtual void position (

record);

const byte *

record ;

Description

This is the position method.

position() is called after each call to rnd_next() if the data needs to be ordered. You can do something like the following to store the position: my_store_ptr(ref, ref_length, current_position);

The server uses ref to store data. ref_length in the above case is the size needed to store current_position. ref is just a byte array that the server will maintain. If you are using offsets to mark rows, then current_position should be the offset. If it is a primary key, then it needs to be a primary key.

Called from filesort.cc, sql_select.cc, sql_delete.cc and sql_update.cc.

Parameters

  • record

Return Values

This method has no return values.

Usage

Return offset or retrieval key information for last row.