# Execution Strategy Execution strategy allows you to change the outcome produced by the rule solver. \ There are several options for the execution strategy described below. ## How to Set Execution Strategy You can set the execution strategy in two ways: * [**Solver API**](https://docs.decisionrules.io/doc/api/rule-solver-api) → by adding the appropriate HTTP header. * [**Test Bench**](https://docs.decisionrules.io/doc/rules/common-rule-features/test-bench) → select the strategy from the dropdown.

Options for Decision Table

Options for Lookup Table

## Allowed Strategies per Rule Type | Rule Type | Allowed Strategies | | -------------------------------- | ------------------------------------------ | | Decision Table | Standard, Array, First Match, Evaluate All | | Decision Tree | Standard, Array | | Scripting Rule | Standard, Array | | Rule Flow | Standard, Array | | Decision Flow + Integration Flow | Standard | | Lookup Table | Lookup Exists, Lookup Value | ## Setting Strategy via API ### Standard Rules Header For all rule types except Lookup Tables, use the `X-Strategy` header to set the execution strategy: | HTTP Header | Possible value | | ----------- | -------------- | | X-Strategy | STANDARD | | X-Strategy | ARRAY | | X-Strategy | FIRST\_MATCH | | X-Strategy | EVALUATE\_ALL | {% hint style="warning" %} If the header is not specified or contains an invalid strategy, the system automatically uses the **STANDARD** strategy. {% endhint %} ### Lookup Table Header Lookup Tables use a dedicated header `X-Lookup-Method` instead of `X-Strategy` : | HTTP Header | Possible value | | --------------- | -------------- | | X-Lookup-Method | LOOKUP\_VALUE | | X-Lookup-Method | LOOKUP\_EXISTS | {% hint style="warning" %} If the header is not specified, the system automatically uses the **LOOKUP\_VALUE** strategy. {% endhint %} ## Strategy Behavior ### Standard Returns all matching rows in the same order as they appear in the rule. If 2 rows are matching the input, the output will contain all matching rows: ```json [ { "client": { "segment": "affluent" }, "profitability": 1 }, { "client": { "segment": "top affluent" }, "profitability": 1.6 } ] ``` #### **Useful for:** * Getting all possible matches for a given input. * Scenarios where multiple rules can apply simultaneously. ### First Match Returns only the first matching row from the rule. Evaluation stops after the first match is found. If 2 rows are matching the input, only the first match is returned: ```json { "client": { "segment": "affluent" }, "profitability": 1 } ``` #### **Useful for:** * Priority-based rules where order matters. * Decision scenarios where only one outcome should apply. {% hint style="info" %} Available for **Decision Tables only**. {% endhint %} ### Array Returns all matching outputs merged into a single object where each output field contains an array of all matched values. If 2 rows are matching the input, the outputs are returned in array format: ```json { "client": { "segment": [ "affluent", "top affluent" ] }, "profitability": [ 1, 1.6 ] } ``` #### **Useful for:** * Aggregating multiple matching results into a single response. * Building lists of applicable values from multiple matches. ### Evaluate All Returns a result for every row in the table regardless of whether it matched or not. Each result includes a `_match` field indicating whether that row was satisfied by the input. ```json [ { "client": { "segment": "affluent" }, "profitability": 1, "_match": true }, { "client": { "segment": "top affluent" }, "profitability": 1.6, "_match": false } ] ``` #### **Useful for:** * Auditing and compliance - see which rules applied and which didn't. * Debugging complex tables with many conditions. * Satisfiability analysis across all rows - table has N rows, the response will contain N objects. {% hint style="info" %} Available for **Decision Tables only**. {% endhint %} ### **Lookup Value** Returns the value found in the Lookup Table that match the input. This is the standard way to retrieve data from a Lookup Table. ```json { "output": "value 1" } // Can return entire row if no column is specified: { "output": { "Primary Key": "inputKey", "column 1": "value 1", "column 2": "value 2" } } ``` #### **Useful for:** * Retrieving actual data stored in the Lookup Table. * Any scenario where you need the actual stored value. For detailed information with examples see Lookup [Value function](https://docs.decisionrules.io/doc/lookup-table/using-lookup-tables-in-rules#lookup_value). {% hint style="info" %} Available for **Lookup Table only**. {% endhint %} ### **Lookup Exists** Returns a boolean indicating whether a matching record exists in the Lookup Table, without returning the actual value. ```json { "output": true } ``` #### **Useful for:** * Validating if a value is in an allowed list. * Checking membership (e.g., is this customer in the VIP list?). * Input validation before processing. * Blacklist/whitelist verification. For detailed information with examples see [Lookup Exist function](https://docs.decisionrules.io/doc/lookup-table/using-lookup-tables-in-rules#lookup_exists). {% hint style="info" %} Available for **Lookup Table only**. {% endhint %}