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.update table command

  • Artikkeli

Applies to: ✅ Microsoft Fabric ✅ Azure Data Explorer

The .update table command performs data updates in a specified table by deleting and appending records atomically.

Warning

This command is unrecoverable.

Note

When you run the .update table command on a table that is the source for an update policy, the .update table command triggers these update policies for which the table being modified is the update policy source.

You can delete up to 5 million records in a single command.

Permissions

You must have at least Table Admin permissions to run this command.

Syntax

Learn more about syntax conventions.

.update [async] table TableName delete DeleteIdentifier append AppendIdentifier [with ( propertyName = propertyValue )] <|
let DeleteIdentifier= DeletePredicate;
let AppendIdentifier= AppendPredicate;

Parameters

Name Type Required Description
async string If specified, indicates that the command runs in asynchronous mode.
TableName string ✔️ The name of the table to update.
DeleteIdentifier string ✔️ The identifier name used to specify the delete predicate applied to the updated table.
DeletePredicate string ✔️ The text of a query whose results are used as data to delete. The predicate has the same limitations as the soft delete predicate.
AppendIdentifier string ✔️ The identifier name used to specify the append predicate applied to the updated table.
AppendPredicate string ✔️ The text of a query whose results are used as data to append.

Important

  • Both delete and append predicates can't use remote entities, cross-db, and cross-cluster entities. Predicates can't reference an external table or use the externaldata operator.
  • Append and delete queries are expected to produce deterministic results. Nondeterministic queries can lead to unexpected results. A query is deterministic if and only if it would return the same data if executed multiple times.
  • Queries might be executed more than once within the update execution. If the intermediate query results are inconsistent, the update command can produce unexpected results.

Supported properties

Name Type Description
whatif bool If true, returns the number of records that will be appended / deleted in every shard, without appending / deleting any records. The default is false.
distributed bool If true, the command ingests from all nodes executing the query in parallel. Default is false. See performance tips.

Important

We recommend running in whatif mode first before executing the update to validate the predicates before deleting or appending data.

Returns

The result of the command is a table where each record represents an extent that was either created with new data or had records deleted.

Name Type Description
Table string The table in which the extent was created or deleted.
Action string Create or Delete depending on the action performed on the extent.
ExtentId guid The unique identifier for the extent created or deleted by the command.
RowCount long The number of rows created or deleted in the specified extent by the command.

Choose between .update table and materialized views

There are scenarios where you could use either the .update table command or a materialized view to achieve the same goal in a table. For example, a materialized view could be used to keep the latest version of each record or an update could be used to update records when a new version is available.

Use the following guidelines to decide which method to use:

  • If your update pattern isn't supported by materialized views, use the update command.
  • If the source table has a high ingestion volume, but only few updates, using the update command can be more performant and consume less cache or storage than materialized views. This is because materialized views need to reprocess all ingested data, which is less efficient than identifying the individual records to update based on the append or delete predicates.
  • Materialized views are a fully managed solution. The materialized view is defined once and materialization happens in the background by the system. The update command requires an orchestrated process (for example, Azure Data Factory, Logic Apps, Power Automate, and others) that explicitly executes the update command every time there are updates. If materialized views work enough for your use case, using materialized views requires less management and maintenance.

Performance tips

  • Data ingestion is a resource-intensive operation that might affect concurrent activities on the cluster, including running queries. We recommend that you avoid the following resource-intensive actions: running many .update commands at once, and intensive use of the distributed property.
  • Limit the append data to less than 1 GB per operation. If necessary, use multiple update commands.
  • Set the distributed flag to true only if the amount of data being produced by the query is large, exceeds 1 GB and doesn't require serialization: multiple nodes can then produce output in parallel. Don't use this flag when query results are small, since it might needlessly generate many small data shards.

Examples

For the examples, we're going to use the following table:

.set-or-replace Employees <|
  range i from 1 to 100 step 1
  | project Id=i
  | extend Code = tostring(dynamic(["Customer", "Employee"])[Id %2])
  | extend Color = tostring(dynamic(["Red", "Blue", "Gray"])[Id %3])

This command creates a table with 100 records starting with:

ID Code Color
1 Employee Blue
2 Customer Gray
3 Employee Red
4 Customer Blue
5 Employee Gray
6 Customer Red
6 Employee Blue

Update a single column on one row

The following example updates a single column on a single row:

.update table Employees delete D append A with(whatif=true) <|
    let D = Employees
      | where Id==3;
    let A = Employees
      | where Id==3
      | extend Color="Orange";

Notice that whatif is set to true. After this query, the table is unchanged, but the command returns that there would be an extent with one row deleted and a new extent with one row.

The following command actually performs the update:

.update table Employees delete D append A <|
    let D = Employees
      | where Id==3;
    let A = Employees
      | where Id==3
      | extend Color="Orange";

Update a single column on multiple rows

The following example updates on one single column Color to the value of Green on those rows that have the value blue.

.update table Employees delete D append A <|
    let D = Employees
        | where Code=="Employee"
        | where Color=="Blue";
    let A = D
      | extend Color="Green";

Here we reused the delete identifier in the definition on the append predicate.

Update multiple columns on multiple rows

The following example updates multiple columns on all rows with color gray.

.update table Employees delete D append A <|
    let D = Employees
      | where Color=="Gray";
    let A = D
      | extend Code=strcat("ex-", Code)
      | extend Color="";

Update rows using another table (reference values)

In this example, the first step is to create the following mapping table:

.set-or-replace ColorMapping <|
  datatable(OldColor:string, NewColor:string)[
    "Red", "Pink",
    "Blue", "Purple",
    "Gray", "LightGray",
    "Orange", "Yellow",
    "Green", "AppleGreen"
  ]

This mapping table is then used to update some colors in the original table:

.update table Employees delete D append A <|
  let D = Employees
    | where Code=="Customer";
  let A = D
    | lookup ColorMapping on $left.Color==$right.OldColor
    | project Id, Code, Color=NewColor

Update rows with a datatable

Sometimes values to update are known without being stored in a table, and the datatable operator can be helpful:

.update table Employees delete D append A <|
  let A = datatable(Id:long, Code:string, Color:string)[
    1, "Customer", "Purple",
    2, "Customer", "Magenta",
    3, "Customer", "Turquoise",
  ];
  let D = Employees
      | join kind=leftsemi A on Id
      | where true;

Update rows with a staging table

A popular pattern is to first land data in a staging table before updating the main table.

The first command creates a staging table:

.set-or-replace MyStagingTable <|
    range i from 70 to 130 step 5
    | project Id=i
    | extend Code = tostring(dynamic(["Customer", "Employee"])[Id %2])
    | extend Color = tostring(dynamic(["Red", "Blue", "Gray"])[Id %3])

The next command updates the main table with the data in the staging table:

.update table Employees delete D append A <|
    let A = MyStagingTable;
    let D = Employees
        | join kind=leftsemi MyStagingTable on Id
        | where true;

Some records in the staging table didn't exist in the main table (that is, had Id>100) but were still inserted in the main table (upsert behavior).

Compound key

The first command creates a table with compound keys:

.set-or-replace VersionedArticle <|
  datatable(ArticleId:string, Version:int, Detail:string)[
    "A", 1, "Early version",
    "B", 1, "News about mobiles",
    "C", 1, "Opinion article",
    "B", 2, "Revision about brand X",
    "B", 3, "Revision about brand Y",
    "C", 2, "Fact check"
  ]

The next command updates a specific record using the expanded syntax:

.update table VersionedArticle delete D append A <|
  let D = VersionedArticle
    | where ArticleId=="B"
    | where Version==3;
  let A = VersionedArticle
    | where ArticleId=="B"
    | where Version==3
    | extend Detail = "Revision about brand Z";

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