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Why this DELETE is so slow?
Message
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Versions des environnements
Visual FoxPro:
VFP 8 SP1
OS:
Windows 2000 SP4
Network:
Windows 2003 Server
Database:
Visual FoxPro
Divers
Thread ID:
00988740
Message ID:
00989043
Vues:
37
Terry,

I know I can change it to Select first and then loop and delete one by one; and it does work faster that way.
However, the question was, what makes it work slow in this particular scenario:
1. It is networked table I delete from
2. It is opened at least one more time by another VFP instance
3. I do not issue FLOCK on it prior to DELETE
4. It has nested SELECT or in some other way requires joining of the table being updated with an intermediate cursor in VFP 9

Because it works fast as it is if
1. It is local table to my machine
2. I do FLOCK first or ensure that it is not opened by anybody else
3. The command dos not involve nested Select

I need to understand what syntax to avoid without running into these performance issues later. And I prefer using standard SQL because of portability issues.

--Andrew
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