MySQL Bug #11757397 49437: CANNOT DO SHOW FIELDS FOR BIG VIEW

revno: 3256

committer: Jon Olav Hauglid <jon.hauglid@oracle.com>

branch nick: mysql-trunk-bug11757397

timestamp: Wed 2011-07-13 12:29:51 +0200

message:

  Bug #11757397 49437: CANNOT DO SHOW FIELDS FOR BIG VIEW

  The problem was that views with too many columns in some

  cases would appear to work correctly, while in other cases gave

  various error messages. For example, DESCRIBE and SHOW commands

  could give "Incorrect key file for table..." errors.

  Depending on column datatypes used, views are materialized

  as either MyISAM or Memory internal temporary tables.

  The root cause of the problem was that MyISAM tables support

  a limited number of columns. This is due too a 64K file header

  size limitation. This limitation was not checked by CREATE VIEW.

  Therefore views with unsupported sizes could be made, leading to

  various errors when the view was later used.

  This patch fixes the problem by reporting ER_TOO_MANY_FIELDS

  error ("Too many columns") if views with more than 4096 columns

  are created. Thus ensuring that any MyISAM table which might

  be created for view processing will fit into the 64K header limit.

  Note that 4096 was chosen as limit as this number is already the

  limit on the number of columns for base tables.

  Test case added to view.test.