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MCOL-271 empty strings should not be NULLs (#2794)

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This patch improves handling of NULLs in textual fields in ColumnStore.
Previously empty strings were considered NULLs and it could be a problem
if data scheme allows for empty strings. It was also one of major
reasons of behavior difference between ColumnStore and other engines in
MariaDB family.

Also, this patch fixes some other bugs and incorrect behavior, for
example, incorrect comparison for "column <= ''" which evaluates to
constant True for all purposes before this patch.
This commit is contained in:
Sergey Zefirov
2023-03-30 17:26:45 +01:00
committed by Roman Nozdrin
parent 0ea592da80
commit b53c231ca6
417 changed files with 12459 additions and 3520 deletions
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18
mysql-test/columnstore/basic/r/mcs219_mid_function.result
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@ -2,7 +2,7 @@ DROP DATABASE IF EXISTS mcs219_db;
CREATE DATABASE mcs219_db;
USE mcs219_db;
CREATE TABLE t1 (a INT, b CHAR(35))ENGINE=Columnstore;
INSERT INTO t1 VALUES (NULL, ''),(1, 'columnstore engine'),(2, 'mariadb database');
INSERT INTO t1 VALUES (NULL, NULL),(1, 'columnstore engine'),(2, 'mariadb database');
SELECT b, MID(b,4,5) FROM t1;
b MID(b,4,5)
NULL NULL
@ -56,21 +56,21 @@ mariadb database ariadb database
SELECT b, MID(b,0,0) FROM t1;
b MID(b,0,0)
NULL NULL
columnstore engine NULL
mariadb database NULL
columnstore engine
mariadb database
SELECT b, MID(b,1,0) FROM t1;
b MID(b,1,0)
NULL NULL
columnstore engine NULL
mariadb database NULL
columnstore engine
mariadb database
SELECT b, MID(b,0,1) FROM t1;
b MID(b,0,1)
NULL NULL
columnstore engine NULL
mariadb database NULL
columnstore engine
mariadb database
SELECT b, MID(b,-1,0) FROM t1;
b MID(b,-1,0)
NULL NULL
columnstore engine NULL
mariadb database NULL
columnstore engine
mariadb database
DROP DATABASE mcs219_db;