percona · WeiHan666 · Jul 10, 2025
diff --git a/mysql-test/suite/innodb/r/extend_varchar_column_compressed_bugfix.result b/mysql-test/suite/innodb/r/extend_varchar_column_compressed_bugfix.result
@@ -0,0 +1,79 @@
+create database database20250708;
+# basic bugfix
+# --------------------------------------------------------------------
+create table database20250708.t11(c1 varchar(253) column_format compressed)CHARACTER SET ascii;
+insert into database20250708.t11 values('qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzR');
+# test from 253 to 254
+alter table database20250708.t11 modify c1 varchar(254) column_format compressed;
+select * from database20250708.t11;
+c1
+qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzR
+SHOW CREATE TABLE database20250708.t11;
+Table	Create Table
+t11	CREATE TABLE `t11` (
+  `c1` varchar(254) /*!50633 COLUMN_FORMAT COMPRESSED */ DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=ascii
+CHECK TABLE database20250708.t11;
+Table	Op	Msg_type	Msg_text
+database20250708.t11	check	status	OK
+alter table database20250708.t11 modify c1 varchar(250) column_format compressed;
+# test from 250 to 255
+alter table database20250708.t11 modify c1 varchar(255) column_format compressed;
+select * from database20250708.t11;
+c1
+qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzR
+SHOW CREATE TABLE database20250708.t11;
+Table	Create Table
+t11	CREATE TABLE `t11` (
+  `c1` varchar(255) /*!50633 COLUMN_FORMAT COMPRESSED */ DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=ascii
+CHECK TABLE database20250708.t11;
+Table	Op	Msg_type	Msg_text
+database20250708.t11	check	status	OK
+# test new threshold 254 in inplace algorithm
+alter table database20250708.t11 modify c1 varchar(256) column_format compressed,algorithm=inplace;
+SHOW CREATE TABLE database20250708.t11;
+Table	Create Table
+t11	CREATE TABLE `t11` (
+  `c1` varchar(256) /*!50633 COLUMN_FORMAT COMPRESSED */ DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=ascii
+CHECK TABLE database20250708.t11;
+Table	Op	Msg_type	Msg_text
+database20250708.t11	check	status	OK
+alter table database20250708.t11 modify c1 varchar(253) column_format compressed;
+alter table database20250708.t11 modify c1 varchar(254) column_format compressed,algorithm=inplace;
+ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY.
+alter table database20250708.t11 modify c1 varchar(252) column_format compressed;
+alter table database20250708.t11 modify c1 varchar(256) column_format compressed,algorithm=inplace;
+ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY.
+# --------------------------------------------------------------------
+# test row log
+# --------------------------------------------------------------------
+alter table database20250708.t11 modify c1 varchar(251) column_format compressed;
+SET DEBUG_SYNC='alter_table_inplace_after_lock_downgrade SIGNAL update_now WAIT_FOR update_done';
+alter table database20250708.t11 modify c1 varchar(253) column_format compressed,algorithm=inplace;
+SET DEBUG_SYNC='now WAIT_FOR update_now';
+insert into database20250708.t11 values('qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRa1');
+begin;
+insert into database20250708.t11 values('qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRa2');
+delete from database20250708.t11;
+rollback;
+begin;
+update database20250708.t11 set c1 = 'qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRgg';
+commit;
+SET DEBUG_SYNC='now SIGNAL update_done';
+SELECT * FROM database20250708.t11;
+c1
+qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRgg
+qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRgg
+SHOW CREATE TABLE database20250708.t11;
+Table	Create Table
+t11	CREATE TABLE `t11` (
+  `c1` varchar(253) /*!50633 COLUMN_FORMAT COMPRESSED */ DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=ascii
+CHECK TABLE database20250708.t11;
+Table	Op	Msg_type	Msg_text
+database20250708.t11	check	status	OK
+# --------------------------------------------------------------------
+# clean up
+drop database database20250708;
diff --git a/mysql-test/suite/innodb/t/extend_varchar_column_compressed_bugfix.test b/mysql-test/suite/innodb/t/extend_varchar_column_compressed_bugfix.test
@@ -0,0 +1,82 @@
+# Fix extend varchar bug with column compressed
+#
+# Author       : Han Wei
+# Date created : 07/08/2025
+
+# Run this test only for debug builds and with debug_sync enabled
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+
+connect (con1,localhost,root,,);
+connection default;
+
+create database database20250708;
+
+--echo # basic bugfix
+--echo # --------------------------------------------------------------------
+create table database20250708.t11(c1 varchar(253) column_format compressed)CHARACTER SET ascii;
+
+insert into database20250708.t11 values('qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzR');
+
+--echo # test from 253 to 254
+alter table database20250708.t11 modify c1 varchar(254) column_format compressed;
+
+select * from database20250708.t11;
+SHOW CREATE TABLE database20250708.t11;
+CHECK TABLE database20250708.t11;
+
+alter table database20250708.t11 modify c1 varchar(250) column_format compressed;
+--echo # test from 250 to 255
+alter table database20250708.t11 modify c1 varchar(255) column_format compressed;
+select * from database20250708.t11;
+SHOW CREATE TABLE database20250708.t11;
+CHECK TABLE database20250708.t11;
+
+--echo # test new threshold 254 in inplace algorithm
+alter table database20250708.t11 modify c1 varchar(256) column_format compressed,algorithm=inplace;
+SHOW CREATE TABLE database20250708.t11;
+CHECK TABLE database20250708.t11;
+
+
+alter table database20250708.t11 modify c1 varchar(253) column_format compressed;
+--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
+alter table database20250708.t11 modify c1 varchar(254) column_format compressed,algorithm=inplace;
+
+
+alter table database20250708.t11 modify c1 varchar(252) column_format compressed;
+--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
+alter table database20250708.t11 modify c1 varchar(256) column_format compressed,algorithm=inplace;
+
+--echo # --------------------------------------------------------------------
+
+
+--echo # test row log
+--echo # --------------------------------------------------------------------
+alter table database20250708.t11 modify c1 varchar(251) column_format compressed;
+
+SET DEBUG_SYNC='alter_table_inplace_after_lock_downgrade SIGNAL update_now WAIT_FOR update_done';
+--send alter table database20250708.t11 modify c1 varchar(253) column_format compressed,algorithm=inplace
+
+
+connection con1;
+SET DEBUG_SYNC='now WAIT_FOR update_now';
+insert into database20250708.t11 values('qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRa1');
+begin;
+insert into database20250708.t11 values('qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRa2');
+delete from database20250708.t11;
+rollback;
+begin;
+update database20250708.t11 set c1 = 'qGjZtLxVfDaKbYOpEUmNRWSiHgBcFpLaQwMrSnTzXyCvJuKdFEaBnCdRgTpMwQfJxHyUvIeOzGkSfNbPkYwVcXzAjLmDtFuQiOWdVjAyKfLpUsXnRzBmQeCiTgHoFvYwZxMkNjGbRaEpCuIdSqTFeYgIuBvNxRzQpSmTkCjHzWdVbYaMlEkFhOjZqUcXiDfPgLaRLpZkYjIxGfEdRcBnAmSqUoWtVhNjKpLmFgCvXzQaByTfEuIzRgg';
+commit;
+
+SET DEBUG_SYNC='now SIGNAL update_done';
+
+connection default;
+--reap
+SELECT * FROM database20250708.t11;
+SHOW CREATE TABLE database20250708.t11;
+CHECK TABLE database20250708.t11;
+
+--echo # --------------------------------------------------------------------
+--echo # clean up
+drop database database20250708;
diff --git a/sql/field.cc b/sql/field.cc
@@ -161,6 +161,7 @@ bool length_prevents_inplace(const Field &from, const Create_field &to) {
        "to.max_display_width_in_bytes():%zu",
        &from, to.field, to.field ? to.field->row_pack_length() : (uint)-1,
        to.max_display_width_in_bytes()));
+  size_t threshold_size = 256;
 
   if (to.pack_length() < from.pack_length()) {
     DBUG_PRINT(
@@ -170,7 +171,13 @@ bool length_prevents_inplace(const Field &from, const Create_field &to) {
     return true;
   }
 
-  if (to.max_display_width_in_bytes() >= 256 && from.row_pack_length() < 256) {
+  if (to.column_format() == COLUMN_FORMAT_TYPE_COMPRESSED &&
+      from.column_format() == COLUMN_FORMAT_TYPE_COMPRESSED) {
+    threshold_size -= INNOBASE_ZIP_COLUMN_HEADER_LENGTH;
+  }
+
+  if (to.max_display_width_in_bytes() >= threshold_size &&
+      from.row_pack_length() < threshold_size) {
     DBUG_PRINT("inplace",
                ("row_pack_length increases past the 256 threshold, from %u to "
                 "%zu, -> true for '%s'",
@@ -179,6 +186,7 @@ bool length_prevents_inplace(const Field &from, const Create_field &to) {
     DBUG_PRINT("inplace",
                ("from:%p, to.field:%p, to.field->row_pack_length():%u", &from,
                 to.field, to.field ? to.field->row_pack_length() : (uint)-1));
+    DBUG_PRINT("inplace", ("threshold_size:%zu", threshold_size));
     return true;
   }
   DBUG_PRINT("inplace", ("-> false"));

diff --git a/sql/field.h b/sql/field.h
@@ -117,6 +117,13 @@ struct timeval;
 */
 #define portable_sizeof_char_ptr 8
 
+/*
+  In InnoDB, the header length of compressed columns is 2 byte. In the
+  SQL layer, this value is needed to determine whether the inplace
+  ddl algorithm can be executed in extending varchar DDL.
+*/
+#define INNOBASE_ZIP_COLUMN_HEADER_LENGTH 2
+
 /*
 
 Field class hierarchy