Add index which nerfs a query run on reservation

Previously doing a full table scan which was executing in about 660ms,
now taking about 10ms.

sql/patches/patch17-idx-pend-reserved.sql

@@ -0,0 +1,63 @@
+-- -----------------------------------------------------------------------------
+-- Hey!
+-- 
+-- This is a new patch-creation script which SHOULD stop double-patching and
+-- running patches out-of-order.
+--
+-- If you're running patches, please close this file, and run this from the 
+-- command line:
+--   $ mysql -u USERNAME -p SCHEMA < patchXX-this-file.sql
+-- where:
+--      USERNAME = a user with CREATE/ALTER access to the schema
+--      SCHEMA = the schema to run the changes against
+--      patch-XX-this-file.sql = this file
+--
+-- If you are writing patches, you need to copy this template to a numbered 
+-- patch file, update the patchversion variable, and add the SQL code to upgrade
+-- the database where indicated below.
+
+DROP PROCEDURE IF EXISTS SCHEMA_UPGRADE_SCRIPT;
+DELIMITER ';;'
+CREATE PROCEDURE SCHEMA_UPGRADE_SCRIPT() BEGIN
+    -- -------------------------------------------------------------------------
+    -- Developers - set the number of the schema patch here!
+    -- -------------------------------------------------------------------------
+    DECLARE patchversion INT DEFAULT 17;
+    -- -------------------------------------------------------------------------
+    -- working variables
+    DECLARE currentschemaversion INT DEFAULT 0;
+    DECLARE lastversion INT;
+
+    -- check the schema has a version table
+    IF NOT EXISTS (SELECT * FROM information_schema.tables WHERE table_name = 'schemaversion' AND table_schema = DATABASE()) THEN
+        SIGNAL SQLSTATE '45000' SET message_text = 'Please ensure patches are run in order! This database does not have a schemaversion table.';
+    END IF;
+
+    -- get the current version
+    SELECT version INTO currentschemaversion FROM schemaversion;
+
+    -- check schema is not ahead of this patch
+    IF currentschemaversion >= patchversion THEN
+        SIGNAL SQLSTATE '45000' SET message_text = 'This patch has already been applied!';
+    END IF;
+
+    -- check schema is up-to-date
+    SET lastversion = patchversion - 1;
+    IF currentschemaversion != lastversion THEN
+		SET @message_text = CONCAT('Please ensure patches are run in order! This patch upgrades to version ', patchversion, ', but the database is not version ', lastversion);
+        SIGNAL SQLSTATE '45000' SET message_text = @message_text;
+    END IF;
+
+    -- -------------------------------------------------------------------------
+    -- Developers - put your upgrade statements here!
+    -- -------------------------------------------------------------------------
+
+    create index pend_reserved on request (reserved);
+
+    -- -------------------------------------------------------------------------
+    -- finally, update the schema version to indicate success
+    UPDATE schemaversion SET version = patchversion;
+END;;
+DELIMITER ';'
+CALL SCHEMA_UPGRADE_SCRIPT();
+DROP PROCEDURE IF EXISTS SCHEMA_UPGRADE_SCRIPT;