[ovs-dev] [PATCH] ovsdb: Force columns that contain weak references to be immutable.
blp at ovn.org
Mon Apr 11 15:14:50 UTC 2016
That sounds reasonable too.
On Mon, Apr 11, 2016 at 05:41:57AM +0000, Elluru, Krishna Mohan wrote:
> Hi Ben,
> If the below idea of allowing NULL values for Indexed columns makes sense., shall we add an attribute (allow_null_index = false kind) as an optional parameter for such type of columns and ensure compatibility with existing/old schema? Does it sound okay?
> Krishna Mohan
> -----Original Message-----
> From: Ben Pfaff [mailto:blp at ovn.org]
> Sent: Monday, April 11, 2016 11:00 AM
> To: Ansari, Shad <shad.ansari at hpe.com>
> Cc: Elluru, Krishna Mohan <elluru.kri.mohan at hpe.com>; dev at openvswitch.org
> Subject: Re: [ovs-dev] [PATCH] ovsdb: Force columns that contain weak references to be immutable.
> On Mon, Apr 04, 2016 at 10:38:40PM +0000, Ansari, Shad wrote:
> > >
> > > HI Ben,
> > > How does column which is weak reference and also configured as an
> > > Index? If it is mutable, and the corresponding UUID going
> > > away(deletion of record) leaves column value as NULL right? And what
> > > would be the behavior if the table is a Root table also?
> > > I am listing down, my assumptions:
> > >
> > > 1. In table X, If the column is index and a weak reference to table
> > > y, on table y row deletion, the index field would become NULL and
> > > since it is an index, constraint violation would occur and to avoid,
> > > it is expected to remove the row first in table X and table Y row
> > > deletion can happen in same txn or consequent transactions. Correct?
> > > 2. If the table X is also a root table, and one of its column is an
> > > index and weak reference to table Y, on row deletion in table Y,
> > > constraint violation would occur, hence similar to above table X row
> > > cleanup is expected to happen prior to table Y row deletion.
> > >
> > > If above 2 statements is true, index with weak reference is
> > > becoming equivalent to strong reference. Am I correct?
> > >
> > > Thanks
> > > Krishna Mohan
> > Would it make sense to allow NULL values for columns that are references and indexes. Something like what MySQL allows for unique keys.
> > http://dev.mysql.com/doc/refman/5.0/en/create-index.html
> That's a reasonable idea. It could theoretically break some currently working use cases, if someone has an OVSDB schema that relies on an index to ensure the uniqueness of an empty column. I don't know whether there are schemas out there that rely on this property.
> I don't know how this idea would extend to multi-column indexes.
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