SQL/MP Version Management Guide

Version Compatibility for SQL Programs

Compaq NonStop™ SQL/MP Version Management Guide—429833-001

7-11

Migrating to a Newer Version

You do not need to recompile an existing SQL program to continue running it on a node

on which the SQL/MP software is upgraded to a newer version. If you do not recompile

the program, the program executes in the same way it did under the older version

software. However, if you do recompile the program, the way in which it is recompiled

can affect the way it executes.

Explicit and Automatic Recompilation

When you recompile a program by running the SQL compiler with a program as an

input, the type of recompilation that takes place is called explicit recompilation. After an

explicit recompilation, the format version of the recompiled program matches the

version of the compiler you are using.

For example, if a program with a format version (PFV) of 2 is recompiled by a version

315 SQL compiler, its PFV is raised to 315. The program then must be executed by a

version 315 or newer executor. If the software on the node where the program is

compiled is subsequently downgraded to an older version, the program can no longer be

executed.

When the SQL compiler recompiles a program or part of a program during execution of

the program, the type of recompilation that takes place is called automatic

recompilation. Automatic recompilation does not change the format version or catalog

version of the recompiled program, because the recompiled object is not stored on disk.

When a program is automatically recompiled, it still can be executed by an older version

SQL executor.

Both kinds of recompilation (explicit and automatic) are performed by the SQL

compiler on the node where the program being recompiled is running.

Upgrading an SQL Compiler by Upgrading a Node

If the SQL/MP software on a node is upgraded to a newer version after an SQL program

is compiled, the version of the SQL compiler on the same node is also upgraded. As a

result, the version of the SQL compiler on the node is newer than the version of the SQL

compiler that originally compiled the program. When this situation occurs, execution is

affected in these ways:

•

Recompilation of a version 2 program by a version 300 or newer SQL compiler does

not cause the operation of the program to change unless the source program uses

new reserved words in column definitions.

Query execution plans might differ, as described under Effect of Newer Version on

Query Execution Plans on page 7-12.

•

Recompilation of a version 1 program by a version 300 or newer compiler does not

cause the operation of the program to change unless the source program includes the

following:

Reserved words in column definitions

Null values in table columns

Queries against changed catalog tables