Re: pglogical_output - a general purpose logical decoding output plugin

The following review has been posted through the commitfest application:
make installcheck-world: not tested
Implements feature: not tested
Spec compliant: not tested
Documentation: not tested

First part of code review (for about 1/3rd of code):
pglogical_output.h:

+ /* Protocol capabilities */
+ #define PGLOGICAL_PROTO_VERSION_NUM 1
+ #define PGLOGICAL_PROTO_MIN_VERSION_NUM 1
Is this protocol version number and minimal recognized version number,
or major and minor version number? I assume that PGLOGICAL_PROTO_VERSION_NUM
is current protocol version (as in config max_proto_version and
min_proto_version). But why we have MIN_VERSION and not MAX_VERSION?

From code in pglogical_output.c (lines 215-225 it looks like
PGLOGICAL_PROTO_VERSION_NUM is maximum, and PGLOGICAL_PROTO_MIN_VERSION_NUM
is treated as minimal protocol version number.

I can see that those constants are exported in pglogical_infofuncs.c and
pglogical.sql, but I do not understand omission of MAX.

+ typedef struct HookFuncName
+ typedef struct PGLogicalTupleData
I haven't found those used anything, and they are not mentioned in
documentation. Are those structures needed?

+ pglogical_config.c:
+ switch(get_param_key(elem->defname))
+ {
+ val = get_param_value(elem, false, OUTPUT_PARAM_TYPE_UINT32);
Why do we need this line here? All cases contain some variant of
val = get_param_value(elem, false, TYPE);
as first line after "case PARAM_*:" so this line should be removed.

+ val = get_param(options, "startup_params_format", false, false,
+ OUTPUT_PARAM_TYPE_UINT32, &found);
+
+ params_format = DatumGetUInt32(val);
Shouldn't we check "found" here? We work with val (which is Datum(0)) - won't
it throw SIGFAULT, or similar?
Additionally - I haven't found any case where code would use "found"
passed from get_param() - so as it's not used it might be removed.

pglogical_output.c:

+ elog(DEBUG1, "Binary mode rejected: Server and client endian sizeof(Datum) mismatch");
+ return false;
+ }
+
+ if (data->client_binary_sizeofint != 0
+ && data->client_binary_sizeofint != sizeof(int))
+ {
+ elog(DEBUG1, "Binary mode rejected: Server and client endian sizeof(int) mismatch");
+ return false;
+ }
+
+ if (data->client_binary_sizeoflong != 0
+ && data->client_binary_sizeoflong != sizeof(long))
+ {
+ elog(DEBUG1, "Binary mode rejected: Server and client endian sizeof(long) mismatch");
Isn't "endian" here case of copy-paste from first error?
Error messages should rather look like:
elog(DEBUG1, "Binary mode rejected: Server and client sizeof(Datum) mismatch");

+ static void pg_decode_shutdown(LogicalDecodingContext * ctx)
In pg_decode_startup we create main memory context, and create hooks memory
context. In pg_decode_shutdown we delete hooks memory context but not main
context. Is this OK, or should we also add:
MemoryContextDelete(data->context);