Add an index on itemData.valueID

Hopefully this will drastically speed up purging after people delete
huge numbers of items.

https://forums.zotero.org/discussion/comment/466885/#Comment_466885

chrome/content/zotero/xpcom/data/items.js

@@ -503,7 +503,7 @@ Zotero.Items = function() {
 		}
 		catch (e) {
 			if (e.message.includes('no such column: IA.authorName')
-					&& await Zotero.DB.valueQueryAsync("SELECT COUNT(*) FROM version WHERE schema='userdata' AND version IN (120, 121)")) {
+					&& await Zotero.DB.valueQueryAsync("SELECT COUNT(*) FROM version WHERE schema='userdata' AND version IN (120, 121, 122)")) {
 				await Zotero.DB.queryAsync("UPDATE version SET version=119 WHERE schema='userdata'");
 				Zotero.crash();
 			}

chrome/content/zotero/xpcom/schema.js

@@ -3455,8 +3455,9 @@ Zotero.Schema = new function(){
 				await Zotero.DB.queryAsync("REPLACE INTO fileTypeMIMETypes VALUES(8, 'application/epub')");
 			}
 			
-			// TEMP: When adding 123, check whether IA.authorName fix in items.js::_loadAnnotations()
-			// can be updated due to update steps being indempodent
+			else if (i == 123) {
+				await Zotero.DB.queryAsync("CREATE INDEX itemData_valueID ON itemData(valueID)");
+			}
 			
 			// If breaking compatibility or doing anything dangerous, clear minorUpdateFrom
 		}

resource/schema/userdata.sql

@@ -1,4 +1,4 @@
--- 122
+-- 123
 
 -- Copyright (c) 2009 Center for History and New Media
 --                    George Mason University, Fairfax, Virginia, USA
@@ -186,6 +186,7 @@ CREATE TABLE itemData (
     FOREIGN KEY (valueID) REFERENCES itemDataValues(valueID)
 );
 CREATE INDEX itemData_fieldID ON itemData(fieldID);
+CREATE INDEX itemData_valueID ON itemData(valueID);
 
 -- Note data for note and attachment items
 CREATE TABLE itemNotes (