Re: Changeset Extraction Interfaces

On 2013-12-12 10:01:21 -0500, Robert Haas wrote:
> On Thu, Dec 12, 2013 at 7:04 AM, Andres Freund <andres@2ndquadrant.com> wrote:
> > I think there'll always be a bit of a difference between slots for
> > physical and logical data, even if 90% of the implementation is the
> > same. We can signal that difference by specifying logical/physical as an
> > option or having two different sets of commands.
> >
> > Maybe?
> >
> > ACQUIRE_REPLICATION_SLOT slot_name PHYSICAL physical_opts
> > ACQUIRE_REPLICATION_SLOT slot_name LOGICAL logical_opts
> > -- already exists without slot, PHYSICAL arguments
> > START_REPLICATION [SLOT slot] [PHYSICAL] RECPTR opt_timeline
> > START_REPLICATION SLOT LOGICAL slot plugin_options
> > RELEASE_REPLICATION_SLOT slot_name
> 
> I assume you meant START_REPLICATION SLOT slot LOGICAL plugin_options,
> but basically this seems OK to me.

When writing the code for this, I decided that I need to reneg a bit on
those names - they don't work nicely enough on the C level for
me. Specifically during a START_REPLICATION we need to temporarily mark
the slot as being actively used and mark it unused again
afterwards. That's much more Acquire/Release like than the persistent
Acquire/Release above for me.

The C names in the version I am working on currently are:
extern void ReplicationSlotCreate(const char *name);
extern void ReplicationSlotDrop(const char *name);
extern void ReplicationSlotAcquire(const char *name);
extern void ReplicationSlotRelease(void);
extern void ReplicationSlotSave(void);

which would make the walsender ones

CREATE_REPLICATION_SLOT ...
START_REPLICATION [SLOT slot] [LOGICAL | PHYSICAL] ...
DROP_REPLICATION_SLOT ...

where START_REPLICATION internally does acquire/release on the passed
SLOT.

Does that work for you?

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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