Re: [PATCH] Reuse Workers and Replication Slots during Logical Replication

Here are some comments for patch v22-0001.

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1. General -- naming conventions

There is quite a lot of inconsistency with variable/parameter naming
styles in this patch. I understand in most cases the names are copied
unchanged from the original functions. Still, since this is a big
refactor anyway, it can also be a good opportunity to clean up those
inconsistencies instead of just propagating them to different places.
IIUC, the usual reluctance to rename things because it would cause
backpatch difficulties doesn't apply here (since everything is being
refactored anyway).

E.g. Consider using use snake_case names more consistently in the
following places:

~

1a. start_table_sync

+static void
+start_table_sync(XLogRecPtr *origin_startpos, char **myslotname)
+{
+ char *syncslotname = NULL;

origin_startpos -> (no change)
myslotname -> my_slot_name (But, is there a better name for this than
calling it "my" slot name)
syncslotname -> sync_slot_name

~

1b. run_tablesync_worker

+static void
+run_tablesync_worker()
+{
+ char originname[NAMEDATALEN];
+ XLogRecPtr origin_startpos = InvalidXLogRecPtr;
+ char *slotname = NULL;
+ WalRcvStreamOptions options;

originname -> origin_name
origin_startpos -> (no change)
slotname -> slot_name

~

1c. set_stream_options

+void
+set_stream_options(WalRcvStreamOptions *options,
+ char *slotname,
+ XLogRecPtr *origin_startpos)
+{
+ int server_version;

options -> (no change)
slotname -> slot_name
origin_startpos -> (no change)
server_version -> (no change)

~

1d. run_apply_worker

static void
-start_apply(XLogRecPtr origin_startpos)
+run_apply_worker()
{
- PG_TRY();
+ char originname[NAMEDATALEN];
+ XLogRecPtr origin_startpos = InvalidXLogRecPtr;
+ char *slotname = NULL;
+ WalRcvStreamOptions options;
+ RepOriginId originid;
+ TimeLineID startpointTLI;
+ char *err;
+ bool must_use_password;

originname -> origin_name
origin_startpos => (no change)
slotname -> slot_name
originid -> origin_id

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src/backend/replication/logical/worker.c

2. SetupApplyOrSyncWorker

-ApplyWorkerMain(Datum main_arg)
+SetupApplyOrSyncWorker(int worker_slot)
{
- int worker_slot = DatumGetInt32(main_arg);
- char originname[NAMEDATALEN];
- XLogRecPtr origin_startpos = InvalidXLogRecPtr;
- char *myslotname = NULL;
- WalRcvStreamOptions options;
- int server_version;
-
- InitializingApplyWorker = true;
-
/* Attach to slot */
logicalrep_worker_attach(worker_slot);

+ Assert(am_tablesync_worker() || am_leader_apply_worker());
+

Why is the Assert not the very first statement of this function?

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Kind Regards,
Peter Smith.
Fujitsu Australia