Placement behavior for temporary table

[lcwangchao]

We should clarify the placement rule behavior on temporary table.

• Create/Update: Placement rule is meaningless for both global and local temporary tables, so we should forbid all placement options when creating or updating a global/local temporary table

• SHOW PLACEMENT: The problem is local temporary table. For local temporary table, it is allowed to have a same name with a normal table in the same database. We should clarify the show behavior. For example, a normal table test.t1 is configured with some placement options and a local temporary table with the same name also exists. What should SHOW PLACEMENT returns? A row display normal table's placement or dismiss this row because a local temporary table exists? I prefer to ignore local temporary table in this situation just like SHOW TABLES .

• SHOW PLACEMENT FOR TABLE : The same problem with SHOW PLACEMENT . But I prefer to use the local temporary table as the target table for this case just like what SHOW CREATE TABLE does. So, for SHOW PLACEMENT FOR TABLE t1, if a local temporary table exists in the current database, it always returns an empty result set ignoring the normal table.

[morgo]

@lcwangchao LGTM, I agree with all 3 behaviors.

[morgo]

I have fixed the first issue in a PR. To fix the 3rd issue the result of the last 2 statements should be the same:

mysql> create temporary table t (a int);
Query OK, 0 rows affected (0.00 sec)

mysql> show placement for table test.t;
Empty set (0.00 sec)

mysql> show placement for table test.nn;
ERROR 1146 (42S02): Table 'test.nn' doesn't exist

[morgo]

Notes:

The PR merged might be a bit simplistic and miss CREATE TABLE LIKE and CREATE GLOBAL TEMPORARY TABLE. We can followup in a further PR.

[morgo]

This has been fixed