Issue creating a KQL materialized view

[pmscorca]

Hi,

I'm testing an eventstream that reads source events from an Azure Event Hubs and write them into a KQL table.

I've created successfully a KQL materialized view (using summarize and arg_max clauses) with the backfill=true option, without specifying the async clause, while the eventstream was active.

After two days, for debug purposes, I've tried to create a parallel materialized view with a different name using the same KQL code and I've obtained this error:

But firts it isn't required the async keyword.

So, I've tried to create an async materialized view using

.create async materialized-view with (backfill=true) mymaterview on table mytable

an OperationId is shown but it doesn't appear any materialized views.

Now, I don't understand because first it isn't necessary to specify the async keyword and then I need to write it.

Then, I don't understand because an async materialized view doesn't appear.

I don't understand because I cannot create a parallel clone materialized view with a different name.

I hope that a materialized view, created with or without the back fill option, keep updating with new source event data without executing any alter action on it.

Any helps to me, please? Many thanks

[v-tangjie-msft · Accepted solution]

Hi @pmscorca ,

It might have seemed like the `async` keyword wasn't required, but for backfill operations, it is mandatory to ensure the process runs in the background without blocking other operations.

When you use the `.create async materialized-view` command, an `OperationId` is generated. You can monitor the progress of this operation using the `.show operations` command. If the materialized view doesn't appear immediately, it might still be processing, especially if the dataset is large.

Here's a step-by-step approach to troubleshoot and resolve your issues:

1. Verify Async Creation:

```kql
.create async materialized-view with (backfill=true) mymaterview on table mytable {
mytable
| summarize arg_max(Timestamp, *) by KeyColumn
}
```

2. Monitor the Operation:

```kql
.show operations
```

3. Make sure the new materialized view name is unique and doesn't conflict with other database objects.

Create materialized view - Kusto | Microsoft Learn

Best Regards,

Neeko Tang

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