Updating Update Policy function while Update Policy is active - azure-data-explorer

Question

Lets say we have a target table TargetTable and we have N different source tables such as SourceTable1, SourceTable2,...,SourceTableN. Now let there be an update policy defined against TargetTable such that every source table feeds to the target table through this update policy. And the common query is a fixed function called TargetTable_loader(). So the output of .show table TargetTable policy update command will look as follows:-
[
{
"IsEnabled": true,
"Source": "SourceTable1",
"Query": "TargetTable_loader()",
"IsTransactional": true,
"PropagateIngestionProperties": false
},
{
"IsEnabled": true,
"Source": "SourceTable2",
"Query": "TargetTable_loader()",
"IsTransactional": true,
"PropagateIngestionProperties": false
},
.
.
.
.
{
"IsEnabled": true,
"Source": "SourceTableN",
"Query": "TargetTable_loader()",
"IsTransactional": true,
"PropagateIngestionProperties": false
}
]
Now, I have the following two questions about this situation.
Since it's a common function for all the (Source,Target) pairs , is there a way for the function to refer to the input table using some generic variable? Because if the function refers to a specific table name , it won't be generic any more. And at the same time if I had to create N different functions that each will refer to a different source table , it will be redundant. Is there a way to parameterize this function with input table name? Something like this:-
.create-or-alter function TargetTable_loader(InputTable:string) { InputTable | ..... }
Secondly , if I have such a common function for mapping all the source tables to the target tables as shown in the initial example -- and say data is being continuously ingested into all the source tables using streaming , what will happen if I abruptly update definition of the common function ? Of course I will ensure that even the new function definition will be valid. But my question is rather focused on whether sudden update of the function , which is being used as query for these N update policies , will affect execution of update policy causing failures merely due the fact that it was abrupt update.

Answer 1

Answers:
You can define a function that receives a table name as a string parameter, and then reference it like this table(tableName):
.create-or-alter function MyFunction(TableName: string) {
table(TableName)
| ...
}
Updating a function used for an update policy won't cause failures (as long as the result schema remains the same).