[#MCOL-4823] WHERE varchar_col<char_col returns a wrong result on a large table

I create a MyISAM table with some string columns with the latin1_bin collation, insert 122881 records and run a query with a WHERE condition which matches all those records:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1

  l_returnflag char(1) CHARACTER SET latin1 COLLATE latin1_bin,

  l_shipinstruct char(25) CHARACTER SET latin1 COLLATE latin1_bin,

  l_comment varchar(44) CHARACTER SET latin1 COLLATE latin1_bin

) ENGINE=MyISAM;

DELIMITER $$

FOR i IN 1..122881

DO

  INSERT INTO t1 VALUES ('a', 'aaaa','AAAA');

END FOR;

$$

DELIMITER ;

SELECT count(*) FROM t1 WHERE l_comment < l_shipinstruct;

It returns all records as expected:

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

| count(*) |

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

|   122881 |

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

Now I make a ColumnStore table with the same structure and data and run the same SELECT query:

DROP TABLE IF EXISTS t2;

CREATE TABLE t2 LIKE t1;

ALTER TABLE t2 ENGINE=ColumnStore;

INSERT INTO t2 SELECT * FROM t1;

SELECT count(*) FROM t2 WHERE l_comment < l_shipinstruct;

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

| count(*) |

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

|        1 |

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

Notice, it returns a wrong result.

Moreover, if I repeat the last query multiple times, it can also return a result like this:

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

| count(*) |

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

|   122880 |

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

But it never returns the expected result 122881.

The problem happens because this method:

SCommand StrFilterCmd::duplicate()

    SCommand ret;

    StrFilterCmd* filterCmd;

    ret.reset(new StrFilterCmd());

    filterCmd = (StrFilterCmd*) ret.get();

    filterCmd->fBOP = fBOP;

    filterCmd->fCompare = fCompare;

    filterCmd->fCharLength = fCharLength;

    return ret;

misses these two lines:

    filterCmd->leftColType = leftColType;

    filterCmd->rightColType = rightColType;

Note, the same method of the parent class, i.e. FilterCommand::duplicate(), does have these two lines!

StrFilterCmd::duplicate() fully duplicates FilterCommand::duplicate() with the exeption that the mentioned two members are not coppied.

To fix this problem and to avoid similar bugs in the future, the duplicate code should be removed.
StrFilterCmd::duplicate() should just call the inherited FilterCommand::duplicate(), then additionally copy its specific members.

[MCOL-4823] WHERE varchar_col<char_col returns a wrong result on a large table Created: 2021-07-29 Updated: 2021-12-10 Resolved: 2021-08-24
Status:	Closed
Project:	MariaDB ColumnStore
Component/s:	PrimProc
Affects Version/s:	6.1.1
Fix Version/s:	6.2.1, 6.2.2

[MCOL-4823] WHERE varchar_col<char_col returns a wrong result on a large table Created: 2021-07-29 Updated: 2021-12-10 Resolved: 2021-08-24