fix PetaPocoExtensions merge
This commit is contained in:
Stephan
@@ -13,27 +13,59 @@ namespace Umbraco.Core.Persistence
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{
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public static class PetaPocoExtensions
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{
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// NOTE
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//
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// proper way to do it with TSQL and SQLCE
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// IF EXISTS (SELECT ... FROM table WITH (UPDLOCK,HOLDLOCK)) WHERE ...)
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// BEGIN
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// UPDATE table SET ... WHERE ...
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// END
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// ELSE
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// BEGIN
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// INSERT INTO table (...) VALUES (...)
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// END
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//
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// works in READ COMMITED, TSQL & SQLCE lock the constraint even if it does not exist, so INSERT is OK
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//
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// proper way to do it with MySQL
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// IF EXISTS (SELECT ... FROM table WHERE ... FOR UPDATE)
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// BEGIN
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// UPDATE table SET ... WHERE ...
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// END
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// ELSE
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// BEGIN
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// INSERT INTO table (...) VALUES (...)
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// END
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//
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// MySQL locks the constraint ONLY if it exists, so INSERT may fail...
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// in theory, happens in READ COMMITTED but not REPEATABLE READ
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// http://www.percona.com/blog/2012/08/28/differences-between-read-committed-and-repeatable-read-transaction-isolation-levels/
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// but according to
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// http://dev.mysql.com/doc/refman/5.0/en/set-transaction.html
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// it won't work for exact index value (only ranges) so really...
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//
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// MySQL should do
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// INSERT INTO table (...) VALUES (...) ON DUPLICATE KEY UPDATE ...
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//
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// also the lock is released when the transaction is committed
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// not sure if that can have unexpected consequences on our code?
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//
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// so... for the time being, let's do with that somewhat crazy solution below...
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/// <summary>
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/// This will handle the issue of inserting data into a table when there can be a violation of a primary key or unique constraint which
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/// can occur when two threads are trying to insert data at the exact same time when the data violates this constraint.
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/// Safely inserts a record, or updates if it exists, based on a unique constraint.
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/// </summary>
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/// <param name="db"></param>
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/// <param name="poco"></param>
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/// <returns>
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/// Returns the action that executed, either an insert or an update
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///
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/// NOTE: If an insert occurred and a PK value got generated, the poco object passed in will contain the updated value.
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/// </returns>
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/// <returns>The action that executed, either an insert or an update. If an insert occurred and a PK value got generated, the poco object
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/// passed in will contain the updated value.</returns>
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/// <remarks>
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/// In different databases, there are a few raw SQL options like MySql's ON DUPLICATE KEY UPDATE or MSSQL's MERGE WHEN MATCHED, but since we are
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/// also supporting SQLCE for which this doesn't exist we cannot simply rely on the underlying database to help us here. So we'll actually need to
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/// try to be as proficient as possible when we know this can occur and manually handle the issue.
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///
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/// We do this by first trying to Update the record, this will return the number of rows affected. If it is zero then we insert, if it is one, then
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/// we know the update was successful and the row was already inserted by another thread. If the rowcount is zero and we insert and get an exception,
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/// that's due to a race condition, in which case we need to retry and update.
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/// <para>We cannot rely on database-specific options such as MySql ON DUPLICATE KEY UPDATE or MSSQL MERGE WHEN MATCHED because SQLCE
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/// does not support any of them. Ideally this should be achieved with proper transaction isolation levels but that would mean revisiting
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/// isolation levels globally. We want to keep it simple for the time being and manage it manually.</para>
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/// <para>We handle it by trying to update, then insert, etc. until something works, or we get bored.</para>
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/// <para>Note that with proper transactions, if T2 begins after T1 then we are sure that the database will contain T2's value
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/// once T1 and T2 have completed. Whereas here, it could contain T1's value.</para>
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/// </remarks>
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internal static RecordPersistenceType InsertOrUpdate<T>(this Database db, T poco)
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where T : class
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@@ -42,155 +74,69 @@ namespace Umbraco.Core.Persistence
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}
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/// <summary>
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/// This will handle the issue of inserting data into a table when there can be a violation of a primary key or unique constraint which
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/// can occur when two threads are trying to insert data at the exact same time when the data violates this constraint.
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/// Safely inserts a record, or updates if it exists, based on a unique constraint.
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/// </summary>
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/// <param name="db"></param>
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/// <param name="poco"></param>
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/// <param name="updateArgs"></param>
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/// <param name="updateCommand">If the entity has a composite key they you need to specify the update command explicitly</param>
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/// <returns>
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/// Returns the action that executed, either an insert or an update
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///
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/// NOTE: If an insert occurred and a PK value got generated, the poco object passed in will contain the updated value.
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/// </returns>
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/// <returns>The action that executed, either an insert or an update. If an insert occurred and a PK value got generated, the poco object
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/// passed in will contain the updated value.</returns>
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/// <remarks>
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/// In different databases, there are a few raw SQL options like MySql's ON DUPLICATE KEY UPDATE or MSSQL's MERGE WHEN MATCHED, but since we are
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/// also supporting SQLCE for which this doesn't exist we cannot simply rely on the underlying database to help us here. So we'll actually need to
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/// try to be as proficient as possible when we know this can occur and manually handle the issue.
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///
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/// We do this by first trying to Update the record, this will return the number of rows affected. If it is zero then we insert, if it is one, then
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/// we know the update was successful and the row was already inserted by another thread. If the rowcount is zero and we insert and get an exception,
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/// that's due to a race condition, in which case we need to retry and update.
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/// <para>We cannot rely on database-specific options such as MySql ON DUPLICATE KEY UPDATE or MSSQL MERGE WHEN MATCHED because SQLCE
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/// does not support any of them. Ideally this should be achieved with proper transaction isolation levels but that would mean revisiting
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/// isolation levels globally. We want to keep it simple for the time being and manage it manually.</para>
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/// <para>We handle it by trying to update, then insert, etc. until something works, or we get bored.</para>
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/// <para>Note that with proper transactions, if T2 begins after T1 then we are sure that the database will contain T2's value
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/// once T1 and T2 have completed. Whereas here, it could contain T1's value.</para>
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/// </remarks>
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internal static RecordPersistenceType InsertOrUpdate<T>(this Database db,
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T poco,
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string updateCommand,
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T poco,
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string updateCommand,
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object updateArgs)
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where T : class
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{
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if (poco == null) throw new ArgumentNullException("poco");
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if (poco == null)
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throw new ArgumentNullException("poco");
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// try to update
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var rowCount = updateCommand.IsNullOrWhiteSpace()
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? db.Update(poco)
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: db.Update<T>(updateCommand, updateArgs);
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if (rowCount > 0) return RecordPersistenceType.Update;
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try
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{
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db.Insert(poco);
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return RecordPersistenceType.Insert;
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}
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//TODO: Need to find out if this is the same exception that will occur for all databases... pretty sure it will be
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catch (SqlException ex)
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{
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//This will occur if the constraint was violated and this record was already inserted by another thread,
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//at this exact same time, in this case we need to do an update
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rowCount = updateCommand.IsNullOrWhiteSpace()
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? db.Update(poco)
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: db.Update<T>(updateCommand, updateArgs);
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if (rowCount == 0)
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{
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//this would be strange! in this case the only circumstance would be that at the exact same time, 3 threads executed, one
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// did the insert and the other somehow managed to do a delete precisely before this update was executed... now that would
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// be real crazy. In that case we need to throw an exception.
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throw new DataException("Record could not be inserted or updated");
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}
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: db.Update<T>(updateCommand, updateArgs);
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if (rowCount > 0)
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return RecordPersistenceType.Update;
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}
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}
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/// <summary>
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/// This will handle the issue of inserting data into a table when there can be a violation of a primary key or unique constraint which
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/// can occur when two threads are trying to insert data at the exact same time when the data violates this constraint.
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/// </summary>
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/// <param name="db"></param>
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/// <param name="poco"></param>
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/// <returns>
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/// Returns the action that executed, either an insert or an update
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///
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/// NOTE: If an insert occurred and a PK value got generated, the poco object passed in will contain the updated value.
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/// </returns>
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/// <remarks>
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/// In different databases, there are a few raw SQL options like MySql's ON DUPLICATE KEY UPDATE or MSSQL's MERGE WHEN MATCHED, but since we are
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/// also supporting SQLCE for which this doesn't exist we cannot simply rely on the underlying database to help us here. So we'll actually need to
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/// try to be as proficient as possible when we know this can occur and manually handle the issue.
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///
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/// We do this by first trying to Update the record, this will return the number of rows affected. If it is zero then we insert, if it is one, then
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/// we know the update was successful and the row was already inserted by another thread. If the rowcount is zero and we insert and get an exception,
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/// that's due to a race condition, in which case we need to retry and update.
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/// </remarks>
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internal static RecordPersistenceType InsertOrUpdate<T>(this Database db, T poco)
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where T : class
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{
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return db.InsertOrUpdate(poco, null, null);
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}
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// failed: does not exist, need to insert
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// RC1 race cond here: another thread may insert a record with the same constraint
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/// <summary>
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/// This will handle the issue of inserting data into a table when there can be a violation of a primary key or unique constraint which
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/// can occur when two threads are trying to insert data at the exact same time when the data violates this constraint.
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/// </summary>
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/// <param name="db"></param>
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/// <param name="poco"></param>
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/// <param name="updateArgs"></param>
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/// <param name="updateCommand">If the entity has a composite key they you need to specify the update command explicitly</param>
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/// <returns>
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/// Returns the action that executed, either an insert or an update
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///
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/// NOTE: If an insert occurred and a PK value got generated, the poco object passed in will contain the updated value.
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/// </returns>
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/// <remarks>
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/// In different databases, there are a few raw SQL options like MySql's ON DUPLICATE KEY UPDATE or MSSQL's MERGE WHEN MATCHED, but since we are
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/// also supporting SQLCE for which this doesn't exist we cannot simply rely on the underlying database to help us here. So we'll actually need to
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/// try to be as proficient as possible when we know this can occur and manually handle the issue.
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///
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/// We do this by first trying to Update the record, this will return the number of rows affected. If it is zero then we insert, if it is one, then
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/// we know the update was successful and the row was already inserted by another thread. If the rowcount is zero and we insert and get an exception,
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/// that's due to a race condition, in which case we need to retry and update.
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/// </remarks>
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internal static RecordPersistenceType InsertOrUpdate<T>(this Database db,
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T poco,
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string updateCommand,
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object updateArgs)
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where T : class
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{
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if (poco == null) throw new ArgumentNullException("poco");
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var rowCount = updateCommand.IsNullOrWhiteSpace()
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? db.Update(poco)
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: db.Update<T>(updateCommand, updateArgs);
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if (rowCount > 0) return RecordPersistenceType.Update;
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try
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var i = 0;
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while (i++ < 4)
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{
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db.Insert(poco);
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return RecordPersistenceType.Insert;
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}
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//TODO: Need to find out if this is the same exception that will occur for all databases... pretty sure it will be
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catch (SqlException ex)
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{
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//This will occur if the constraint was violated and this record was already inserted by another thread,
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//at this exact same time, in this case we need to do an update
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rowCount = updateCommand.IsNullOrWhiteSpace()
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? db.Update(poco)
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: db.Update<T>(updateCommand, updateArgs);
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if (rowCount == 0)
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try
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{
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//this would be strange! in this case the only circumstance would be that at the exact same time, 3 threads executed, one
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// did the insert and the other somehow managed to do a delete precisely before this update was executed... now that would
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// be real crazy. In that case we need to throw an exception.
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throw new DataException("Record could not be inserted or updated");
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// try to insert
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db.Insert(poco);
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return RecordPersistenceType.Insert;
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}
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catch (SqlException) // TODO: need to find out if all db will throw that exception - probably OK
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{
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// failed: exists (due to race cond RC1)
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// RC2 race cond here: another thread may remove the record
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return RecordPersistenceType.Update;
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// try to update
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rowCount = updateCommand.IsNullOrWhiteSpace()
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? db.Update(poco)
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: db.Update<T>(updateCommand, updateArgs);
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if (rowCount > 0)
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return RecordPersistenceType.Update;
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// failed: does not exist (due to race cond RC2), need to insert
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// loop
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}
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}
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// this can go on forever... have to break at some point and report an error.
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throw new DataException("Record could not be inserted or updated.");
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}
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/// <summary>
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