minor #15354 Added indexes to sql commands used to create session tables (JohnstonCode)

This PR was merged into the 4.4 branch.

Discussion
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Added indexes to sql commands used to create session tables

As per https://github.com/symfony/symfony/blob/4.4/UPGRADE-4.4.md#httpfoundation `PdoSessionHandler` now precalculates the expiry timestamp in the lifetime column, so the index will speed up garbage collection

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Commits
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b9f84c8 Added indexes to sql commands used to create session tables

Author: javiereguiluz

session/database.rst

@@ -393,7 +393,8 @@ MariaDB/MySQL
         `sess_id` VARBINARY(128) NOT NULL PRIMARY KEY,
         `sess_data` BLOB NOT NULL,
         `sess_lifetime` INTEGER UNSIGNED NOT NULL,
-        `sess_time` INTEGER UNSIGNED NOT NULL
+        `sess_time` INTEGER UNSIGNED NOT NULL,
+        INDEX `sessions_sess_lifetime_idx` (`sess_lifetime`)
     ) COLLATE utf8mb4_bin, ENGINE = InnoDB;
 
 .. note::
@@ -414,6 +415,7 @@ PostgreSQL
         sess_lifetime INTEGER NOT NULL,
         sess_time INTEGER NOT NULL
     );
+    CREATE INDEX sessions_sess_time_idx ON sessions (sess_lifetime);
 
 Microsoft SQL Server
 ....................
@@ -424,7 +426,8 @@ Microsoft SQL Server
         sess_id VARCHAR(128) NOT NULL PRIMARY KEY,
         sess_data NVARCHAR(MAX) NOT NULL,
         sess_lifetime INTEGER NOT NULL,
-        sess_time INTEGER NOT NULL
+        sess_time INTEGER NOT NULL,
+        INDEX sessions_sess_lifetime_idx (sess_lifetime)
     );
 
 Store Sessions in a NoSQL Database (MongoDB)