[fdo-internals] FDO RFC 16 - FDO Provider for SQLite

[Orest Halustchak]

Hi Traian,

Just catching up on this email thread ...

To support transactions, the commit must ensure that everything that should be persisted is written to the file (the Durable part of ACID). For Rollback, SQLite may do the rollback for you, but if you have anything in memory that was modified by the transaction, you'll have to back out those changes, e.g. in your in-memory spatial index. So, yes, somebody can just call the FDO SQL command, but the provider may need to be aware of when commit and rollback are called.

Also, for this provider, how is the db to be shared between users? Is it single writer, multiple reader? On multiple reader, how is the spatial index to be shared?

Thanks,
Orest.

-----Original Message-----
From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Traian Stanev
Sent: Tuesday, March 18, 2008 4:12 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] FDO RFC 16 - FDO Provider for SQLite


SQLite is ACID (for some value of ACID). I'm not sure what's involved in supporting transactions properly, but feature commands (insert/update/select) will internally be done using transactions anyway. With insert, one pretty much has to batch lots of inserts into one transaction, because a write transaction in SQLite involves closing and reopening the file -- which is a very slow way to coordinate access. Anyway, it really depends on what the most often used access pattern would be for such an FDO provider. So I guess the answer is "yes, if necessary, we can have explicit transaction support"? Also, keep in mind that you can start a transaction at any time using the FDO SQL command, then go on and execute some other feature commands, and end it by a commit.


Traian


-----Original Message-----
From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Jason Birch
Sent: Tuesday, March 18, 2008 3:55 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] FDO RFC 16 - FDO Provider for SQLite

Traian,

I think you may have missed addressing Mateusz' question about
transactions.  Considering that SQLite is (apparently) ACID, wouldn't it
make sense to support these?

Jason

-----Original Message-----
From: Traian Stanev
Subject: [fdo-internals] FDO RFC 16 - FDO Provider for SQLite

I think my reply to RFC 16 questions got sent to the bit bucket, so here
it is, again:
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