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SQL Generation Steps for OuterApply

See original GitHub issue

Hi,

Shorter version: Found out today that Serenity picks OUTER APPLY clause in its query builder before it goes for LEFT JOIN values in XyzRow.cs class, causing errors (there is a workaround causing more data reads than needed).

Longer version: So in practical terms, if we have a LeftJoin on a property in XyzRow.cs class and want to use that left join in OuterApply to limit data reads, Serenity throws a SQL error:

The multi-part identifier "jLeftJoinedTable.foreign_key_column" could not be bound.

That means, instead of generating a SQL with main tables and Property LeftJoins first e.g. the expected SQL would be:

SELECT * FROM [schema].[main_table] AS T0
LEFT JOIN [schema].[property_table] AS jLeftJoinedTable ON T0.foreign_key_column = jLeftJoinedTable.foreign_key_column
OUTER APPLY
(
	SELECT DISTINCT
		[outer_table].[column_id],
		[outer_table].[column_name],
		[outer_table].[effected_date]
	FROM [schema].[some_other_table] AS [outer_table]
	WHERE jLeftJoinedTable.outer_table_related_id = outer_table.id
)outerTable

The generated code for XyzRow.cs class actually comes out as.

SELECT * FROM [schema].[main_table] AS T0
OUTER APPLY
(
	SELECT DISTINCT
		[outer_table].[column_id],
		[outer_table].[column_name],
		[outer_table].[effected_date]
	FROM [schema].[some_other_table] AS [outer_table]
	WHERE jLeftJoinedTable.outer_table_related_id = outer_table.id
)outerTable
LEFT JOIN [schema].[property_table] AS jLeftJoinedTable ON T0.foreign_key_column = jLeftJoinedTable.foreign_key_column

This causes The multi-part identifier error mentioned above.

The workaround would be to force more data reads than necessary:

[OuterApply("outerTable", @"
	SELECT DISTINCT
		[outer_table].[column_id],
		[outer_table].[column_name],
		[outer_table].[effected_date]
	FROM [schema].[some_other_table] AS [outer_table]
	LEFT JOIN [schema].[a_third_table] AS [unnecessary_joined_table] ON outerTable.column = unnecessary_joined_table.column
	LEFT JOIN [schema].[main_table] AS T1 ON a_third_table.some_column = T1.some_column
	LEFT JOIN [schema].[property_table] AS jLeftJoinedTable ON T1.foreign_key_column = jLeftJoinedTable.foreign_key_column
	WHERE jLeftJoinedTable.outer_table_related_id = outer_table.id
"])
// XyzRow code..

This makes for a painful SQL where we’d want just a setting label etc.

Interestingly, if we bypass List() method of XyzRepository.cs class and instead follow this:

[OuterApply("outerTable", @"
	SELECT DISTINCT
		[outer_table].[column_id],
		[outer_table].[column_name],
		[outer_table].[effected_date]
	FROM [schema].[some_other_table] AS [outer_table]
	WHERE jLeftJoinedTable.outer_table_related_id = outer_table.id
")]
// XyzRow code..

Then in XyzRepository.cs create a method:

List<XyzRow> CustomListMethod()
{

	// Get latest by create datetime descending.
	void action(SqlQuery query)
	{
		query.Distinct(true);
		query.SelectTableFields();
		query.SelectNonTableFields();
		// query.DebugText.Dump("--List OuContractWeeklyActivityEventRow"); <= checked in LINQPad 6
		//query.ToString().Dump("--GetOUsByPostAssignment");
	}

	List<XyzRow> rows = null;
	using (var connection = SqlConnections.NewByKey(fld.ConnectionKey))
	{
		rows = connection.List<XyzRow>(action);		
	}
	return rows;
}

// XyzRepository code...

Then the SQL is correctly generated as:

SELECT * FROM [schema].[main_table] AS T0
LEFT JOIN [schema].[property_table] AS jLeftJoinedTable ON T0.foreign_key_column = jLeftJoinedTable.foreign_key_column
OUTER APPLY
(
	SELECT DISTINCT
		[outer_table].[column_id],
		[outer_table].[column_name],
		[outer_table].[effected_date]
	FROM [schema].[some_other_table] AS [outer_table]
	WHERE jLeftJoinedTable.outer_table_related_id = outer_table.id
)outerTable

Please can this be looked into? Will save us from creating unnecessary CustomList() methods in repositories.

Kind Regards.