[2pt] Add columns to existing tables in SQL

[TarantoolBot]

Add columns to existing tables in SQL

Product: Tarantool (SQL)
Since: 2.7.1
Audience/target: Tarantool users
Root document: https://www.tarantool.io/en/doc/latest/reference/reference_sql/sql_statements_and_clauses/#alter-table
SME: @romanhabibov
Peer reviewer: @

Details

Now, it is possible to add columns to existing empty spaces using
<ALTER TABLE table_name ADD [COLUMN] column_name column_type ...>
statement. The column definition is the same as in
statement.

• Space emptiness is Tarantool's restriction. Possibilty to add
  column to non empty space will be implemented later.

For example:

tarantool> box.execute("CREATE TABLE test (a INTEGER PRIMARY KEY)")
---
- row_count: 1
...

tarantool> box.execute([[ALTER TABLE test ADD COLUMN b TEXT
         >                                           CHECK (LENGTH(b) > 1)
         >                                           NOT NULL
         >                                           DEFAULT ('aa')
         >                                           COLLATE "unicode_ci"
         >             ]])
---
- row_count: 1
...

Requested by @romanhabibov in tarantool/tarantool@6cff902.

[pgulutzan]

@romanhabibov: This is only in version 2.7, right?

[Totktonada]

Yep, since 2.7.0-38-g6cff90259.

[pgulutzan]

I changed version 2.6 adding a note that there is a plan to allow more. I will change version 2.7 when it exists.

[veod32]

I changed version 2.6 adding a note that there is a plan to allow more. I will change version 2.7 when it exists.

Now, the 2.6 documentation branch is not in the use. There will be no 2.7 branch, so all the updates should be done in the latest branch which is the default one now. As I can see, your commit is already in the latest branch.

I think you can make final documentation updates according to this issue description: functional changes mentioned there are not planned, they are already implemented in the 2.7.1 release. After making doc updates, please ask @NickVolynkin or @veod32 for the peer review of your pull request.