mirror of
https://github.com/mariadb-corporation/mariadb-columnstore-engine.git
synced 2025-05-01 08:44:47 +03:00
b53c231ca6
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.
57 lines
873 B
Plaintext
57 lines
873 B
Plaintext
DROP DATABASE IF EXISTS mcs37_db;
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CREATE DATABASE mcs37_db;
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USE mcs37_db;
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CREATE TABLE t1(col1 INT, col2 CHAR(5))ENGINE=Columnstore;
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INSERT INTO t1 VALUES(NULL, NULL),(1,'a'),(1,'b'),(1,'c'),(2,'dd'),(3,'eee');
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SELECT COUNT(DISTINCT col1) FROM t1;
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COUNT(DISTINCT col1)
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3
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SELECT COUNT(DISTINCT col2) FROM t1;
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COUNT(DISTINCT col2)
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5
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SELECT DISTINCT col1 FROM t1;
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col1
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NULL
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1
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2
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3
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SELECT DISTINCT col1 FROM t1 ORDER BY col1 DESC;
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col1
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3
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2
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1
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NULL
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SELECT DISTINCT col2 FROM t1;
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col2
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NULL
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a
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b
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c
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dd
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eee
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CREATE TABLE t2(col1 INT)ENGINE=Columnstore;
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INSERT INTO t2 SELECT DISTINCT col1 FROM t1;
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SELECT * FROM t2;
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col1
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NULL
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1
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2
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3
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CREATE TABLE t3 (name varchar(255));
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INSERT INTO t3 VALUES ('aa'),('ab'),('ac'),('ad'),('ae');
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SELECT DISTINCT * FROM t3;
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name
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aa
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ab
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ac
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ad
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ae
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SELECT DISTINCT name FROM t3 LIMIT 2;
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name
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aa
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ab
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SELECT DISTINCT 1 FROM t3 LIMIT 3;
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1
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1
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DROP DATABASE mcs37_db;
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