* Turn -[SPMySQLConnection checkConnectionIfNecessary] into a public method, since it is actually the preferable way to -[SPMySQLConnection checkConnection] (which forces network IO in a new thread each time)

* Change `-[SPDatabaseStructure queryDbStructureWithUserInfo:]` doing a forced connection check inside a tight loop (#2306)

Author: dmoagx

Frameworks/SPMySQLFramework/Source/SPMySQL Private APIs.h

@@ -47,7 +47,6 @@
 - (void)_disconnect;
 - (void)_updateConnectionVariables;
 - (void)_restoreConnectionVariables;
-- (BOOL)_checkConnectionIfNecessary;
 - (void)_validateThreadSetup;
 + (void)_removeThreadVariables:(NSNotification *)aNotification;
 

Frameworks/SPMySQLFramework/Source/SPMySQLConnection Categories/Querying & Preparation.m

@@ -79,7 +79,7 @@ - (NSString *)escapeString:(NSString *)theString includingQuotes:(BOOL)includeQu
 	// Ensure per-thread variables are set up
 	[self _validateThreadSetup];
 
-	if (![self _checkConnectionIfNecessary]) return nil;
+	if (![self checkConnectionIfNecessary]) return nil;
 
 	// Perform a lossy conversion to bytes, using NSData to do the hard work.  Preserves
 	// nul characters correctly.
@@ -259,7 +259,7 @@ - (id)queryString:(NSString *)theQueryString usingEncoding:(NSStringEncoding)the
 	[self _validateThreadSetup];
 
 	// Check the connection if necessary, returning nil if the state couldn't be validated
-	if (![self _checkConnectionIfNecessary]) return nil;
+	if (![self checkConnectionIfNecessary]) return nil;
 
 	// Determine whether a maximum query size needs to be restored from a previous query
 	if (queryActionShouldRestoreMaxQuerySize != NSNotFound) {

Frameworks/SPMySQLFramework/Source/SPMySQLConnection Categories/Server Info.m

@@ -107,7 +107,7 @@ - (SPMySQLResult *)listProcesses
 	if (state != SPMySQLConnected) return nil;
 
 	// Check the connection if appropriate
-	if (![self _checkConnectionIfNecessary]) return nil;
+	if (![self checkConnectionIfNecessary]) return nil;
 
 	// Lock the connection before using it
 	[self _lockConnection];
@@ -153,7 +153,7 @@ - (BOOL)killQueryOnThreadID:(unsigned long)theThreadID
 
 - (BOOL)serverShutdown
 {
-	if([self _checkConnectionIfNecessary]) {
+	if([self checkConnectionIfNecessary]) {
 		[self _lockConnection];
 		// Ensure per-thread variables are set up
 		[self _validateThreadSetup];

Frameworks/SPMySQLFramework/Source/SPMySQLConnection.h

@@ -188,6 +188,7 @@
 - (BOOL)isConnected;
 - (BOOL)isConnectedViaSSL;
 - (BOOL)checkConnection;
+- (BOOL)checkConnectionIfNecessary;
 - (double)timeConnected;
 - (BOOL)userTriggeredDisconnect;
 

Frameworks/SPMySQLFramework/Source/SPMySQLConnection.m

@@ -336,6 +336,8 @@ - (BOOL)isConnectedViaSSL
  *
  * WARNING: This method may return NO if the current thread is cancelled!
  *          You MUST check the isCancelled flag before using the result!
+ *
+ * NOTE: In general -checkConnectionIfNecessary should be used instead!
  */
 - (BOOL)checkConnection
 {
@@ -374,6 +376,35 @@ - (BOOL)checkConnection
 	return connectionVerified;
 }
 
+/**
+ * If thirty seconds have passed since the last time the connection was
+ * used, check the connection.
+ * This minimises the impact of continuous additional connection checks -
+ * each of which requires a round trip to the server - but handles most
+ * network issues.
+ * Returns whether the connection is considered still valid.
+ *
+ * WARNING: This method may return NO if the current thread is cancelled!
+ *          You MUST check the isCancelled flag before using the result!
+ */
+- (BOOL)checkConnectionIfNecessary
+{
+	
+	// If the connection has been dropped in the background, trigger a
+	// reconnect and return the success state here
+	if (state == SPMySQLConnectionLostInBackground) {
+		return [self _reconnectAllowingRetries:YES];
+	}
+	
+	// If the connection was recently used, return success
+	if (_elapsedSecondsSinceAbsoluteTime(lastConnectionUsedTime) < 30) {
+		return YES;
+	}
+	
+	// Otherwise check the connection
+	return [self checkConnection];
+}
+
 /**
  * Retrieve the time elapsed since the connection was established, in seconds.
  * This time is retrieved in a monotonically increasing fashion and is high
@@ -1042,35 +1073,6 @@ - (void)_restoreConnectionVariables
 	[self setEncodingUsesLatin1Transport:encodingUsesLatin1Transport];
 }
 
-/**
- * If thirty seconds have passed since the last time the connection was
- * used, check the connection.
- * This minimises the impact of continuous additional connection checks -
- * each of which requires a round trip to the server - but handles most
- * network issues.
- * Returns whether the connection is considered still valid.
- *
- * WARNING: This method may return NO if the current thread is cancelled!
- *          You MUST check the isCancelled flag before using the result!
- */
-- (BOOL)_checkConnectionIfNecessary
-{
-
-	// If the connection has been dropped in the background, trigger a
-	// reconnect and return the success state here
-	if (state == SPMySQLConnectionLostInBackground) {
-		return [self _reconnectAllowingRetries:YES];
-	}
-
-	// If the connection was recently used, return success
-	if (_elapsedSecondsSinceAbsoluteTime(lastConnectionUsedTime) < 30) {
-		return YES;
-	}
-
-	// Otherwise check the connection
-	return [self checkConnection];
-}
-
 /**
  * Ensure that the thread this method is called on has been registered for
  * use with MySQL.  MySQL requires thread-specific variables for safe

Source/SPDatabaseStructure.m

@@ -551,7 +551,7 @@ - (BOOL)_ensureConnectionUnsafe
 	if (!mySQLConnection || !delegate) return NO;
 
 	// Check the connection state
-	if ([mySQLConnection isConnected] && [mySQLConnection checkConnection]) return YES;
+	if ([mySQLConnection isConnected] && [mySQLConnection checkConnectionIfNecessary]) return YES;
 
 	// the result of checkConnection may be meaningless if the thread was cancelled during execution. (issue #2353)
 	if([[NSThread currentThread] isCancelled]) return NO;