Horton

Re: Minimal logical decoding on standbys

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Jeff Davis <pgsql@j-davis.com>, Thomas Munro <thomas.munro@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, fabriziomello@gmail.com, tushar <tushar.ahuja@enterprisedb.com>, Rahila Syed <rahila.syed@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Melanie Plageman <melanieplageman@gmail.com>
Date: 2023-04-04T05:57:02Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Reduce the log level in 035_standby_logical_decoding.pl.

  2. 035_standby_logical_decoding: Add missing waits for replication

  3. For cascading replication, wake physical and logical walsenders separately

  4. Handle logical slot conflicts on standby

  5. Support invalidating replication slots due to horizon and wal_level

  6. Prevent use of invalidated logical slot in CreateDecodingContext()

  7. Replace replication slot's invalidated_at LSN with an enum

  8. Pass down table relation into more index relation functions

  9. Assert only valid flag bits are passed to visibilitymap_set()

  10. Remove unused _bt_delitems_delete() argument.

  11. Add xl_btree_delete optimization.

On Mon, Apr 3, 2023 at 8:51 PM Drouvot, Bertrand
<bertranddrouvot.pg@gmail.com> wrote:
>
> On 4/2/23 10:10 PM, Andres Freund wrote:
> > Hi,
> >>              restart_lsn = s->data.restart_lsn;
> >> -
> >> -            /*
> >> -             * If the slot is already invalid or is fresh enough, we don't need to
> >> -             * do anything.
> >> -             */
> >> -            if (XLogRecPtrIsInvalid(restart_lsn) || restart_lsn >= oldestLSN)
> >> +            slot_xmin = s->data.xmin;
> >> +            slot_catalog_xmin = s->data.catalog_xmin;
> >> +
> >> +            /* the slot has been invalidated (logical decoding conflict case) */
> >> +            if ((xid && ((LogicalReplicationSlotIsInvalid(s)) ||
> >> +            /* or the xid is valid and this is a non conflicting slot */
> >> +                                     (TransactionIdIsValid(*xid) && !(LogicalReplicationSlotXidsConflict(slot_xmin, slot_catalog_xmin, *xid))))) ||
> >> +            /* or the slot has been invalidated (obsolete LSN case) */
> >> +                    (!xid && (XLogRecPtrIsInvalid(restart_lsn) || restart_lsn >= oldestLSN)))
> >>              {
> >
> > This still looks nearly unreadable. I suggest moving comments outside of the
> > if (), remove redundant parentheses, use a function to detect if the slot has
> > been invalidated.
> >
>
> I made it as simple as:
>
>          /*
>           * If the slot is already invalid or is a non conflicting slot, we don't
>           * need to do anything.
>           */
>          islogical = xid ? true : false;
>
>          if (SlotIsInvalid(s, islogical) || SlotIsNotConflicting(s, islogical, xid, &oldestLSN))
>
> in V56 attached.
>

Here the variable 'islogical' doesn't seem to convey its actual
meaning because one can imagine that it indicates whether the slot is
logical which I don't think is the actual intent. One idea to simplify
this is to introduce a single function CanInvalidateSlot() or
something like that and move the logic from both the functions
SlotIsInvalid() and SlotIsNotConflicting() into the new function.

-- 
With Regards,
Amit Kapila.