mirror of
https://github.com/MariaDB/server.git
synced 2025-01-16 12:02:42 +01:00
103 lines
2.6 KiB
Text
103 lines
2.6 KiB
Text
set @subselect_mat_cost=@@optimizer_switch;
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set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
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set long_query_time=0.1;
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drop database if exists world;
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set names utf8;
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create database world;
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use world;
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CREATE TABLE Country (
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Code char(3) NOT NULL default '',
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Name char(52) NOT NULL default '',
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SurfaceArea float(10,2) NOT NULL default '0.00',
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Population int(11) NOT NULL default '0',
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Capital int(11) default NULL,
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PRIMARY KEY (Code),
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UNIQUE INDEX (Name)
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);
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CREATE TABLE City (
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ID int(11) NOT NULL auto_increment,
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Name char(35) NOT NULL default '',
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Country char(3) NOT NULL default '',
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Population int(11) NOT NULL default '0',
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PRIMARY KEY (ID),
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INDEX (Population),
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INDEX (Country)
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);
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CREATE TABLE CountryLanguage (
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Country char(3) NOT NULL default '',
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Language char(30) NOT NULL default '',
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Percentage float(3,1) NOT NULL default '0.0',
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PRIMARY KEY (Country, Language),
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INDEX (Percentage)
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);
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Make the schema and data more diverse by adding more indexes, nullable
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columns, and NULL data.
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create index SurfaceArea on Country(SurfaceArea);
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create index Language on CountryLanguage(Language);
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create index CityName on City(Name);
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alter table City change population population int(11) null default 0;
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select max(id) from City into @max_city_id;
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insert into City values (@max_city_id + 1,'Kilifarevo','BGR',NULL);
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SELECT COUNT(*) FROM Country;
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COUNT(*)
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239
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SELECT COUNT(*) FROM City;
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COUNT(*)
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4080
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SELECT COUNT(*) FROM CountryLanguage;
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COUNT(*)
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984
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set @@optimizer_switch = 'exists_to_in=on,in_to_exists=on,semijoin=on,materialization=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on';
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1. Subquery in a disjunctive WHERE clause of the outer query.
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Q1.1m:
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MATERIALIZATION: there are too many rows in the outer query
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to be looked up in the inner table.
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EXPLAIN
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SELECT Name FROM Country
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WHERE (EXISTS (select 1 from City where City.Population > 100000 and
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Code = Country) OR
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Name LIKE 'L%') AND
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surfacearea > 1000000;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country ALL Name,SurfaceArea NULL NULL NULL 239 Using where
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2 MATERIALIZED City ALL Population,Country NULL NULL NULL 4080 Using where
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SELECT Name FROM Country
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WHERE (EXISTS (select 1 from City where City.Population > 100000 and
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Code = Country) OR
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Name LIKE 'L%') AND
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surfacearea > 1000000;
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Name
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Algeria
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Angola
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Argentina
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Australia
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Bolivia
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Brazil
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Egypt
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South Africa
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Ethiopia
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Indonesia
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India
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Iran
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Canada
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Kazakstan
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China
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Colombia
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Congo, The Democratic Republic of the
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Libyan Arab Jamahiriya
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Mali
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Mauritania
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Mexico
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Mongolia
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Niger
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Peru
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Saudi Arabia
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Sudan
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Chad
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Russian Federation
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United States
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drop database world;
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set optimizer_switch=@subselect_mat_cost;
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