Simple way to simulate a bug in logical replication

[Avi Weinberg <AviW@xxxxxxxxx>]

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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