rdbms: Remove outdated MySQL 4 references and fix doc URLs

- Remove or clarify ancient comments referencing MySQL 4.

- Oracle can't afford to host small HTML files for longer than two
  years, as such they make a point to break their URLs after a while.
  Update our references to the last 5.x release for now, where the same
  information resides (instead 404 or redirect to MySQL 8 docs).

Bug: T34217
Change-Id: I322cc8936f96c2545c63e7c9c1f5fa241e2b8c18

includes/installer/MysqlUpdater.php

@@ -496,8 +496,8 @@ class MysqlUpdater extends DatabaseUpdater {
 	}
 
 	/**
-	 * 1.4 betas were missing the 'binary' marker from logging.log_title,
-	 * which causes a collation mismatch error on joins in MySQL 4.1.
+	 * MW 1.4 betas were missing the 'binary' marker from logging.log_title,
+	 * which caused a MySQL collation mismatch error.
 	 *
 	 * @param string $table Table name
 	 * @param string $field Field name to check

includes/libs/rdbms/database/Database.php

@@ -3213,12 +3213,13 @@ abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAware
 	}
 
 	/**
-	 * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
-	 * is only needed because a) MySQL must be as efficient as possible due to
-	 * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
-	 * which index to pick. Anyway, other databases might have different
-	 * indexes on a given table. So don't bother overriding this unless you're
-	 * MySQL.
+	 * USE INDEX clause.
+	 *
+	 * This can be used as optimisation in queries that affect tables with multiple
+	 * indexes if the database does not pick the most optimal one by default.
+	 * The "right" index might vary between database backends and versions thereof,
+	 * as such in practice this is biased toward specifically improving performance
+	 * of large wiki farms that use MySQL or MariaDB (like Wikipedia).
 	 *
 	 * @stable to override
 	 * @param string $index
@@ -3229,12 +3230,9 @@ abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAware
 	}
 
 	/**
-	 * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
-	 * is only needed because a) MySQL must be as efficient as possible due to
-	 * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
-	 * which index to pick. Anyway, other databases might have different
-	 * indexes on a given table. So don't bother overriding this unless you're
-	 * MySQL.
+	 * IGNORE INDEX clause.
+	 *
+	 * The inverse of Database::useIndexClause.
 	 *
 	 * @stable to override
 	 * @param string $index

includes/libs/rdbms/database/DatabaseMysqlBase.php

@@ -155,7 +155,7 @@ abstract class DatabaseMysqlBase extends Database {
 				$set[] = 'sql_mode = ' . $this->addQuotes( $this->sqlMode );
 			}
 			// Set any custom settings defined by site config
-			// (e.g. https://dev.mysql.com/doc/refman/4.1/en/innodb-parameters.html)
+			// https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html
 			foreach ( $this->connectionVariables as $var => $val ) {
 				// Escape strings but not numbers to avoid MySQL complaining
 				if ( !is_int( $val ) && !is_float( $val ) ) {
@@ -260,7 +260,7 @@ abstract class DatabaseMysqlBase extends Database {
 		// Unfortunately, mysql_fetch_object does not reset the last errno.
 		// Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 		// these are the only errors mysql_fetch_object can cause.
-		// See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
+		// See https://dev.mysql.com/doc/refman/5.7/en/mysql-fetch-row.html.
 		if ( $errno == 2000 || $errno == 2013 ) {
 			throw new DBUnexpectedError(
 				$this,
@@ -293,7 +293,7 @@ abstract class DatabaseMysqlBase extends Database {
 		// Unfortunately, mysql_fetch_array does not reset the last errno.
 		// Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 		// these are the only errors mysql_fetch_array can cause.
-		// See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
+		// See https://dev.mysql.com/doc/refman/5.7/en/mysql-fetch-row.html.
 		if ( $errno == 2000 || $errno == 2013 ) {
 			throw new DBUnexpectedError(
 				$this,
@@ -329,7 +329,7 @@ abstract class DatabaseMysqlBase extends Database {
 		// Unfortunately, mysql_num_rows does not reset the last errno.
 		// We are not checking for any errors here, since
 		// there are no errors mysql_num_rows can cause.
-		// See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
+		// See https://dev.mysql.com/doc/refman/5.7/en/mysql-fetch-row.html.
 		// See https://phabricator.wikimedia.org/T44430
 		return $n;
 	}
@@ -1230,8 +1230,8 @@ abstract class DatabaseMysqlBase extends Database {
 	}
 
 	/**
-	 * FROM MYSQL DOCS:
-	 * https://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_release-lock
+	 * See
+	 * https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_release-lock
 	 * @param string $lockName
 	 * @param string $method
 	 * @return bool

includes/page/WikiPage.php

@@ -740,7 +740,7 @@ class WikiPage implements Page, IDBAccessObject {
 			// SELECT. Thus we need S1 to also gets the revision row FOR UPDATE; otherwise, it
 			// may not find it since a page row UPDATE and revision row INSERT by S2 may have
 			// happened after the first S1 SELECT.
-			// https://dev.mysql.com/doc/refman/5.0/en/set-transaction.html#isolevel_repeatable-read
+			// https://dev.mysql.com/doc/refman/5.7/en/set-transaction.html#isolevel_repeatable-read
 			$revision = $this->getRevisionStore()
 				->getRevisionByPageId( $this->getId(), $latest, RevisionStore::READ_LOCKING );
 		} elseif ( $this->mDataLoadedFrom == self::READ_LATEST ) {

includes/search/SearchMySQL.php

@@ -27,7 +27,7 @@
 use MediaWiki\MediaWikiServices;
 
 /**
- * Search engine hook for MySQL 4+
+ * Search engine hook for MySQL
  * @ingroup Search
  */
 class SearchMySQL extends SearchDatabase {

maintenance/archives/patch-logging-title.sql

@@ -1,5 +1,5 @@
--- 1.4 betas were missing the 'binary' marker from logging.log_title,
--- which causes a collation mismatch error on joins in MySQL 4.1.
+-- MW 1.4 betas were missing the 'binary' marker from logging.log_title,
+-- which causes a MySQL collation mismatch error.
 
 ALTER TABLE /*$wgDBprefix*/logging
   CHANGE COLUMN log_title

maintenance/archives/patch-testrun.sql

@@ -4,8 +4,6 @@
 -- and comparisons of what's changed from the previous run will be
 -- displayed at the end of each run.
 --
--- These tables currently require MySQL 5 (or maybe 4.1?) for subselects.
---
 
 drop table if exists /*$wgDBprefix*/testitem;
 drop table if exists /*$wgDBprefix*/testrun;