[MDEV-16134] Wrong I_S.COLUMNS.CHARACTER_XXX_LENGTH value for compressed columns - Jira

This script queries I_S for a latin1 compressed varchar column:

CREATE OR REPLACE TABLE t1 (a VARCHAR(10) CHARACTER SET latin1 COMPRESSED);

SELECT

  CHARACTER_MAXIMUM_LENGTH, CHARACTER_OCTET_LENGTH

FROM

  INFORMATION_SCHEMA.COLUMNS

WHERE

  TABLE_SCHEMA='test' AND TABLE_NAME='t1' AND COLUMN_NAME='a';

+--------------------------+------------------------+

| CHARACTER_MAXIMUM_LENGTH | CHARACTER_OCTET_LENGTH |

+--------------------------+------------------------+

|                       11 |                     11 |

+--------------------------+------------------------+

11 looks wrong. The expected value would be 10 for both columns.

Now trying an utf8 column:

CREATE OR REPLACE TABLE t1 (a VARCHAR(10) CHARACTER SET utf8 COMPRESSED);

SELECT

  CHARACTER_MAXIMUM_LENGTH, CHARACTER_OCTET_LENGTH

FROM

  INFORMATION_SCHEMA.COLUMNS

WHERE

  TABLE_SCHEMA='test' AND TABLE_NAME='t1' AND COLUMN_NAME='a';

+--------------------------+------------------------+

| CHARACTER_MAXIMUM_LENGTH | CHARACTER_OCTET_LENGTH |

+--------------------------+------------------------+

|                       10 |                     31 |

+--------------------------+------------------------+

The value for CHARACTER_OCTET_LENGTH is wrong. The expected result is 30.

relates to

MDEV-15592 Column COMPRESSED should select a 'high order' datatype

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