--- title: "Background queries" description: "Learn how to execute asynchronous background queries using the Aerospike Go client on primary and secondary indexes." --- # Background queries > For the complete documentation index see: [llms.txt](https://aerospike.com/docs/llms.txt) > > All documentation pages available in markdown. Jump to the [Code block](#code-block) for a combined complete example. A client application can also issue an asynchronous background query to the database and apply a series of write [transaction operations](https://aerospike.com/docs/develop/client/go/usage/multi/batch) to each record. This is more efficient than a query to retrieve records followed by updates to them for cases where data needs to be manipulated on the client side. Transactional operations are typically more efficient than using Lua UDFs because the server doesn’t need to translate internal objects to another language. Many client libraries also provide an API to poll for the completion of a background query. Refer to [Background Queries](https://aerospike.com/docs/develop/learn/queries/primary-index#background-queries) for more information. ## Setup The following examples will use the setup and record structure below to illustrate background queries in an Aerospike database. ```go import ( "fmt" "github.com/aerospike/aerospike-client-go/v6" ) // Establishes a connection to the server client, err := aerospike.NewClient("127.0.0.1", 3000) if err != nil { log.Fatal(err) } defer client.Close() ``` The record structure: ```asciidoc Occurred: Integer Reported: Integer Posted: Integer Report: Map { shape: List, summary: String, city: String, state: String, duration: String } Location: GeoJSON ``` ## Policies Background queries can define policies to pass to the executed task. The following example creates a policy that defines a filter expression looking for records that do not already have a `numShapes` bin. ```go // Create new write policy writePolicy := aerospike.NewWritePolicy(0,0) writePolicy.FilterExpression = aerospike.ExpNot( aerospike.ExpBinExists("numShapes")) ``` ## Query Just like [basic queries](https://aerospike.com/docs/develop/client/go/usage/multi/queries/basic) background queries can be run on the primary index or, using a filter, on a secondary index. ### Primary index The following example creates a primary index background query using the Filter Expression defined in the policies example to find all records without a `numShapes` bin, then get the length of the `shape` key in the `report` map and write that value to a new bin called `numShapes`. ```go // Create statement stmt := aerospike.NewStatement("sandbox", "ufodata") exp := aerospike.ExpListSize( aerospike.ExpMapGetByKey(aerospike.MapReturnType.VALUE, aerospike.ExpTypeLIST, aerospike.ExpStringVal("shape"), aerospike.ExpMapBin("report"))) task, err := client.QueryExecute(nil, writePolicy, stmt, aerospike.ExpWriteOp("numShapes", exp, aerospike.ExpWriteFlagDefault)) if err != nil { log.Fatal(err) } ``` ### Secondary index The following example uses a [secondary index](https://aerospike.com/docs/develop/client/go/usage/multi/queries/secondary#create-an-index) created on the `occurred` bin. ```plaintext asadm -e 'enable; manage sindex create numeric occurred_idx ns sandbox set ufodata bin occurred' ``` Then creates a secondary index background query using a Filter Expression checking for the existence of a `posted` bin on records that have an `occurred` bin value inclusively between `20210101` and `20211231`, that updates the `report` map by adding a `recent` key with a value of `true`. ```go // Create new write policy writePolicy := aerospike.NewWritePolicy(0,0) writePolicy.FilterExpression = aerospike.ExpBinExists("posted") // Create statement stmt := aerospike.NewStatement("sandbox", "ufodata") // Set index filter stmt.SetFilter(aerospike.NewRangeFilter("occurred", 20210101, 20211231)) task, err := client.QueryExecute(nil, writePolicy, stmt, aerospike.MapPutOp(aerospike.DefaultMapPolicy(), "report", aerospike.NewValue("recent"), aerospike.NewValue(true))) if err != nil { log.Fatal(err) } ``` ## Tracking Once a background query has been executed, a query status can be obtained to query nodes for task completion. ```go // Return the query status status, err := task.IsDone(); if err != nil { // Handle error } else { if status { fmt.Printf("Query complete") } else { fmt.Printf("Query in progress") } } ``` ## Code block Expand this section for a single code block to execute a background query ```go import ( "fmt" "github.com/aerospike/aerospike-client-go/v6" ) func main() { // Establishes a connection to the server client, err := aerospike.NewClient("127.0.0.1", 3000) if err != nil { log.Fatal(err) } defer client.Close() writePolicy := aerospike.NewWritePolicy(0,0) writePolicy.FilterExpression = aerospike.ExpNot( aerospike.ExpBinExists("numShapes")) // Create statement stmt := aerospike.NewStatement("sandbox", "ufodata") exp := aerospike.ExpListSize( aerospike.ExpMapGetByKey(aerospike.MapReturnType.VALUE, aerospike.ExpTypeLIST, aerospike.ExpStringVal("shape"), aerospike.ExpMapBin("report"))) task, err := client.QueryExecute(nil, writePolicy, stmt, aerospike.ExpWriteOp("numShapes", exp, aerospike.ExpWriteFlagDefault)) if err != nil { log.Fatal(err) } status, err := task.IsDone(); if err != nil { // Handle error } else { if status { fmt.Printf("Query complete") } else { fmt.Printf("Query in progress") } } } ```