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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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2
mysql-test/columnstore/basic/r/mcs81_self_join.result
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@ -2,7 +2,7 @@ DROP DATABASE IF EXISTS mcs81_db;
CREATE DATABASE mcs81_db;
USE mcs81_db;
CREATE TABLE t1 (t1_col1 INT, t1_col2 TEXT)ENGINE=Columnstore;
INSERT INTO t1 VALUES (NULL, '');
INSERT INTO t1 VALUES (NULL, NULL);
INSERT INTO t1 VALUES (1, repeat('a', 20)),(3, repeat('c', 20)),(5, repeat('a', 20)),(7, repeat('c', 20)),(9, repeat('a', 20));
SELECT * FROM t1 AS a, t1 AS b WHERE a.t1_col1 = b.t1_col1;
t1_col1 t1_col2 t1_col1 t1_col2