[#MCOL-4579] CHAR(2) NULL: empty strings or SPACE(N) get converted to NULL

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a CHAR(2) DEFAULT '') ENGINE=ColumnStore;

INSERT INTO t1 VALUES ('');

INSERT INTO t1 VALUES (' ');

INSERT INTO t1 VALUES ('  ');

SELECT HEX(a) FROM t1;

+--------+

| HEX(a) |

+--------+

| NULL   |

| NULL   |

| NULL   |

+--------+

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a CHAR(2) DEFAULT 'aa') ENGINE=ColumnStore;

INSERT INTO t1 VALUES ('');

INSERT INTO t1 VALUES (' ');

INSERT INTO t1 VALUES ('  ');

SELECT HEX(a) FROM t1;

+--------+

| HEX(a) |

+--------+

| NULL   |

| NULL   |

| NULL   |

+--------+

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a CHAR(2) DEFAULT ' ') ENGINE=ColumnStore;

INSERT INTO t1 VALUES ('');

INSERT INTO t1 VALUES (' ');

INSERT INTO t1 VALUES ('  ');

SELECT HEX(a) FROM t1;

+--------+

| HEX(a) |

+--------+

| NULL   |

| NULL   |

| NULL   |

+--------+

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a CHAR(2) DEFAULT '  ') ENGINE=ColumnStore;

INSERT INTO t1 VALUES ('');

INSERT INTO t1 VALUES (' ');

INSERT INTO t1 VALUES ('  ');

SELECT HEX(a) FROM t1;

+--------+

| HEX(a) |

+--------+

| NULL   |

| NULL   |

| NULL   |

+--------+

In all above cases, empty strings as well as strings consisting only of space characters were replaced to NULL. Looks wrong.

Also, inserting an empty string should:

either store NULL for now (like it does)
or store the true empty string (when we fix the flaw that an empty string is NULL)

[MCOL-4579] CHAR(2) NULL: empty strings or SPACE(N) get converted to NULL Created: 2021-03-04 Updated: 2023-07-25 Resolved: 2023-04-25
Status:	Closed
Project:	MariaDB ColumnStore
Component/s:	PrimProc
Affects Version/s:	5.5.1
Fix Version/s:	N/A