15.19.4 InnoDB memcached Multiple get and Range Query Support

Table des matières

The daemon_memcached plugin supports multiple get operations (fetching multiple key-value pairs in a single memcached query) and range queries.

Multiple get Operations

The ability to fetch multiple key-value pairs in a single memcached query improves read performance by reducing communication traffic between the client and server. For InnoDB, it means fewer transactions and open-table operations.

The following example demonstrates multiple-get support. The example uses the test.city table described in Creating a New Table and Column Mapping.

mysql> USE test;
mysql> SELECT * FROM test.city;
+---------+-----------+-------------+---------+-------+------+--------+
| city_id | name | state | country | flags | cas | expiry |
+---------+-----------+-------------+---------+-------+------+--------+
| B | BANGALORE | BANGALORE | IN | 0 | 1 | 0 |
| C | CHENNAI | TAMIL NADU | IN | 0 | 0 | 0 |
| D | DELHI | DELHI | IN | 0 | 0 | 0 |
| H | HYDERABAD | TELANGANA | IN | 0 | 0 | 0 |
| M | MUMBAI | MAHARASHTRA | IN | 0 | 0 | 0 |
+---------+-----------+-------------+---------+-------+------+--------+

Run a get command to retrieve all values from the city table. The results are returned in a key-value pair sequence.

telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
get B C D H M
VALUE B 0 22
BANGALORE|BANGALORE|IN
VALUE C 0 21
CHENNAI|TAMIL NADU|IN
VALUE D 0 14
DELHI|DELHI|IN
VALUE H 0 22
HYDERABAD|TELANGANA|IN
VALUE M 0 21
MUMBAI|MAHARASHTRA|IN
END

When retrieving multiple values in a single get command, you can switch tables (using @@containers.name notation) to retrieve the value for the first key, but you cannot switch tables for subsequent keys. For example, the table switch in this example is valid:

get @@aaa.AA BB
VALUE @@aaa.AA 8 12
HELLO, HELLO
VALUE BB 10 16
GOODBYE, GOODBYE
END

Attempting to switch tables again in the same get command to retrieve a key value from a different table is not supported.

Table des matières Haut

Range Queries

For range queries, the daemon_memcached plugin supports the following comparison operators: <, >, <=, >=. An operator must be preceded by an @ symbol. When a range query finds multiple matching key-value pairs, results are returned in a key-value pair sequence.

The following examples demonstrate range query support. The examples use the test.city table described in Creating a New Table and Column Mapping.

mysql> SELECT * FROM test.city;
+---------+-----------+-------------+---------+-------+------+--------+
| city_id | name | state | country | flags | cas | expiry |
+---------+-----------+-------------+---------+-------+------+--------+
| B | BANGALORE | BANGALORE | IN | 0 | 1 | 0 |
| C | CHENNAI | TAMIL NADU | IN | 0 | 0 | 0 |
| D | DELHI | DELHI | IN | 0 | 0 | 0 |
| H | HYDERABAD | TELANGANA | IN | 0 | 0 | 0 |
| M | MUMBAI | MAHARASHTRA | IN | 0 | 0 | 0 |
+---------+-----------+-------------+---------+-------+------+--------+

Open a telnet session:

telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.

To get all values greater than B, enter get @>B:

get @>B
VALUE C 0 21
CHENNAI|TAMIL NADU|IN
VALUE D 0 14
DELHI|DELHI|IN
VALUE H 0 22
HYDERABAD|TELANGANA|IN
VALUE M 0 21
MUMBAI|MAHARASHTRA|IN
END

To get all values less than M, enter get @<M:

get @<M
VALUE B 0 22
BANGALORE|BANGALORE|IN
VALUE C 0 21
CHENNAI|TAMIL NADU|IN
VALUE D 0 14
DELHI|DELHI|IN
VALUE H 0 22
HYDERABAD|TELANGANA|IN
END

To get all values less than and including M, enter get @<=M:

get @<=M
VALUE B 0 22
BANGALORE|BANGALORE|IN
VALUE C 0 21
CHENNAI|TAMIL NADU|IN
VALUE D 0 14
DELHI|DELHI|IN
VALUE H 0 22
HYDERABAD|TELANGANA|IN
VALUE M 0 21
MUMBAI|MAHARASHTRA|IN

To get values greater than B but less than M, enter get @>B@<M:

get @>B@<M
VALUE C 0 21
CHENNAI|TAMIL NADU|IN
VALUE D 0 14
DELHI|DELHI|IN
VALUE H 0 22
HYDERABAD|TELANGANA|IN
END

A maximum of two comparison operators can be parsed, one being either a 'less than' (@<) or 'less than or equal to' (@<=) operator, and the other being either a 'greater than' (@>) or 'greater than or equal to' (@>=) operator. Any additional operators are assumed to be part of the key. For example, if you issue a get command with three operators, the third operator (@>C) is treated as part of the key, and the get command searches for values smaller than M and greater than B@>C.

get @<M@>B@>C
VALUE C 0 21
CHENNAI|TAMIL NADU|IN
VALUE D 0 14
DELHI|DELHI|IN
VALUE H 0 22
HYDERABAD|TELANGANA|IN

Rechercher dans le manuel MySQL

Traduction non disponible

Le manuel MySQL n'est pas encore traduit en français sur l'infobrol. Seule la version anglaise est disponible pour l'instant.

Document créé le 26/06/2006, dernière modification le 26/10/2018
Source du document imprimé : https://www.gaudry.be/mysql-rf-innodb-memcached-multiple-get-range-query.html

L'infobrol est un site personnel dont le contenu n'engage que moi. Le texte est mis à disposition sous licence CreativeCommons(BY-NC-SA). Plus d'info sur les conditions d'utilisation et sur l'auteur.

Références

Manuel MySQL : https://dev.mysql.com/

Ces références et liens indiquent des documents consultés lors de la rédaction de cette page, ou qui peuvent apporter un complément d'information, mais les auteurs de ces sources ne peuvent être tenus responsables du contenu de cette page.
L'auteur de ce site est seul responsable de la manière dont sont présentés ici les différents concepts, et des libertés qui sont prises avec les ouvrages de référence. N'oubliez pas que vous devez croiser les informations de sources multiples afin de diminuer les risques d'erreurs.

Table des matières Haut