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I create a test file with this content:
-- source include/have_binlog_format_row.inc
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-- source include/master-slave.inc
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connection master;
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let mst=LONGBLOB COMPRESSED;
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let slv=MEDIUMBLOB;
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let cnv='ALL_LOSSY';
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# This is to make sure that the compressed data is longer than 64K
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SET column_compression_threshold=16*256*256;
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--eval CREATE TABLE t1 (a $mst);
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sync_slave_with_master;
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connection slave;
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SET @tmp=@@GLOBAL.SLAVE_TYPE_CONVERSIONS;
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eval SET GLOBAL SLAVE_TYPE_CONVERSIONS = $cnv;
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--eval ALTER TABLE t1 MODIFY a $slv;
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connection master;
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INSERT INTO t1 (a) VALUES (REPEAT('a',256*256));
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SELECT LENGTH(a) FROM t1;
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sync_slave_with_master;
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SHOW CREATE TABLE t1;
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SELECT LENGTH(a) FROM t1;
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connection master;
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DROP TABLE t1;
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sync_slave_with_master;
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connection slave;
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SET GLOBAL SLAVE_TYPE_CONVERSIONS=@tmp;
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--source include/rpl_end.inc
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It creates a wrong output:
--------------------------------------------------------------------------
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worker[1] Using MTR_BUILD_THREAD 300, with reserved ports 16000..16019
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include/master-slave.inc
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[connection master]
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connection master;
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SET column_compression_threshold=16*256*256;
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CREATE TABLE t1 (a LONGBLOB COMPRESSED);;
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connection slave;
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connection slave;
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SET @tmp=@@GLOBAL.SLAVE_TYPE_CONVERSIONS;
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SET GLOBAL SLAVE_TYPE_CONVERSIONS = 'ALL_LOSSY';
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ALTER TABLE t1 MODIFY a MEDIUMBLOB;;
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connection master;
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INSERT INTO t1 (a) VALUES (REPEAT('a',256*256));
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SELECT LENGTH(a) FROM t1;
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LENGTH(a)
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65536
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connection slave;
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SHOW CREATE TABLE t1;
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Table Create Table
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t1 CREATE TABLE `t1` (
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`a` mediumblob DEFAULT NULL
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) ENGINE=MyISAM DEFAULT CHARSET=latin1
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SELECT LENGTH(a) FROM t1;
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LENGTH(a)
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0
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connection master;
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DROP TABLE t1;
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connection slave;
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connection slave;
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SET GLOBAL SLAVE_TYPE_CONVERSIONS=@tmp;
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include/rpl_end.inc
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compat/oracle.AAA2 'row' [ pass ] 1035
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--------------------------------------------------------------------------
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Notice, LENGTH(a) is 65536 on the master side, while 0 on the slave side.
Note, if I change REPEAT('a',256*255) to REPEAT('a',256*250) to make length fit into two bytes, it start to work fine and return 64000 both on master and slave side.
The problem most likely resides in this piece of the code:
Field *Type_handler_blob_compressed::make_conversion_table_field(TABLE *table,
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uint metadata,
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const Field *target)
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const
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{
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return new(table->in_use->mem_root)
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Field_blob_compressed(Record_addr(true), Field::NONE,
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&empty_clex_str,
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table->s, 2, target->charset(),
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zlib_compression_method);
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}
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Notice, it always creates a field with packlength=2. It should pass 1, 2, 3 or 4 depending on the exact BLOB type on the master side (TINYBLOB, BLOB, MEDIUMBLOB, LONGBLOB).
The exact data type can be read from metadata.
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