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MDEV-16290 ALTER TABLE ... RENAME COLUMN syntax

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The existing syntax for renaming a column uses "ALTER TABLE ...  CHANGE"
command. This requires full column specification to rename the column.
This patch adds new syntax "ALTER TABLE ...  RENAME COLUMN", which do not
expect users to provide full column specification.  It means that the new
syntax would pick in-place or copy algorithm in the same way as that of
existing "ALTER TABLE ... CHANGE" command. The existing syntax
"ALTER TABLE ... CHANGE" will continue to work.

Syntax changes
==============

ALTER TABLE tbl_name
    [alter_specification [, alter_specification] ...]
    [partition_options]

Following is a new <alter_specification> added:

 | RENAME COLUMN <oldname> TO <newname>

Where <oldname> and <newname> are identifiers for old name and new
name of the column.

Related to: WL#10761
This commit is contained in:
Aleksey Midenkov
2020-03-03 13:50:32 +03:00
parent a99c93a7fa
commit fa8ad75439
10 changed files with 656 additions and 34 deletions
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14
sql/sql_class.h
View File

@ -333,17 +333,25 @@ public:
class Alter_column :public Sql_alloc {
public:
const char *name;
LEX_CSTRING name;
LEX_CSTRING new_name;
Virtual_column_info *default_value;
bool alter_if_exists;
Alter_column(const char *par_name, Virtual_column_info *expr, bool par_exists)
:name(par_name), default_value(expr), alter_if_exists(par_exists) {}
Alter_column(LEX_CSTRING par_name, Virtual_column_info *expr, bool par_exists)
:name(par_name), new_name{NULL, 0}, default_value(expr), alter_if_exists(par_exists) {}
Alter_column(LEX_CSTRING par_name, LEX_CSTRING _new_name)
:name(par_name), new_name(_new_name), default_value(NULL), alter_if_exists(false) {}
/**
Used to make a clone of this object for ALTER/CREATE TABLE
@sa comment for Key_part_spec::clone
*/
Alter_column *clone(MEM_ROOT *mem_root) const
{ return new (mem_root) Alter_column(*this); }
bool is_rename()
{
DBUG_ASSERT(!new_name.str || !default_value);
return new_name.str;
}
};