I think VFP figured out how to handle multi-user concurrent updates a long time ago... At least until MS broke SMB... Multiple times... 😊
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rk
-----Original Message----- From: ProfoxTech [mailto:profoxtech-bounces@leafe.com] On Behalf Of Stephen Russell Sent: Thursday, January 25, 2018 2:05 PM To: profoxtech@leafe.com Subject: Re: Indexes on VFP tables--when do they get updated
I see a potential problem when multiple users are doing updates on the same table. What constitutes the server file to be updated? How do the localized cdx files know to update when the server version is updated?
On Thu, Jan 25, 2018 at 12:51 PM, Gene Wirchenko genew@telus.net wrote:
At 08:15 2018-01-25, mbsoftwaresolutions@mbsoftwaresolutions.com wrote:
On 2018-01-24 18:39, Fernando D. Bozzo wrote:
When the index is evaluated initially, VFP knows exactly what fields affect what index, so really just affected indexes are updated. It's easy to test it. just make an old index (IDX) on two different fields: CREATE TABLE test (field1 C(10), field2 I) INDEX on field1 TO test_f1 additive INDEX on field2 TO test_f2 additive Add some data, wait a minute, replace one of the fields and do a FLUSH FORCE, and you will see that only the affected index changes his timestamp.
I don't think that's a fair test to use IDX files since this example uses
a CDX file, and it's all in the same file.
I think it *is* a fair test for exactly that reason. If you see onlyone of the IDX index files change, that suggests that VFP only updates an index where it would make a difference.
I grant that it could be that that optimisation does not exist in theCDX handling, but how likely do you think that is?
Sincerely,
Gene Wirchenko
[excessive quoting removed by server]
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