RE: [External] Simple way to simulate a bug in logical replication

[Avi Weinberg]

Please note:
I tried it also with Postgres 15.6 and the behavior is the same
I'm running inside docker.  I do not know if it matters...

Hi All,

I think I hit a bug in logical replication in version 15.2.  I sync two tables 
of size 305MB but pg_stat_progress_copy shows that 5GB as bytes_processed and 
the sync takes forever.
Is this a bug?  If so, what can I do with this scenario?

Thanks

Create a dummy table

CREATE TABLE example_table (
    id SERIAL PRIMARY KEY,
    binary_data BYTEA
);

Create a function that inserts a row of few MB into the table
CREATE OR REPLACE FUNCTION generate_large_data()
RETURNS BYTEA AS $$
DECLARE
    large_data BYTEA;
BEGIN
    large_data := decode(repeat('DEADBEEF', 102400000), 'hex');
    RETURN large_data;
END;
$$ LANGUAGE plpgsql;

I Inserted this sample row 112 times
INSERT INTO example_table (binary_data) VALUES (generate_large_data());

Checked that table size
SELECT pg_size_pretty(pg_total_relation_size('example_table'));
The table size was  305MB

I added this table to logical replication (and another table called 
example_table1 that had similar structure and data.
I run the following command
select * from pg_stat_progress_copy

I got that bytes_processed for each of the tables is over 5GB

"pid","datid","datname","relid","command","type","bytes_processed","bytes_total","tuples_processed","tuples_excluded","pg_size_pretty"
599,16384,"aaa_db",19833,"COPY FROM","CALLBACK","5898403943","0","13","0","5625 
MB"
597,16384,"aa_db",19824,"COPY FROM","CALLBACK","5898403938","0","13","0","5625 
MB"


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