> ## Documentation Index
> Fetch the complete documentation index at: https://docs.therefrain.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Memory Operations

> Accumulate and aggregate data across steps using memory collections.

## Overview

**Memory operations** let you collect and summarize data across multiple steps or loop iterations. Data is stored in named **collections** that persist throughout the execution.

## Two operation types

| Type        | Description                         | Use case                                  |
| ----------- | ----------------------------------- | ----------------------------------------- |
| `append`    | Add an item to a collection         | Accumulate rows, records, captured values |
| `aggregate` | Compute a summary over a collection | Sum totals, count items, find min/max     |

## Append

Add a captured value to a named collection:

```yaml theme={null}
steps:
  - ordinal: 0
    description: "Extract product data"
    action:
      type: extract
      script: "document.querySelector('.product-name').textContent"
    url: "https://app.example.com/products"
    riskLevel: low
    requiresConfirmation: false
    captures:
      - name: productName
        strategy: snapshot
        description: "Product name"
    memoryOperations:
      - type: append
        collection: products
        source: productName
```

| Field        | Type       | Required | Description                     |
| ------------ | ---------- | :------: | ------------------------------- |
| `type`       | `"append"` |    Yes   | Operation type                  |
| `collection` | string     |    Yes   | Target collection name          |
| `source`     | string     |    No    | Capture variable name to append |

## Aggregate

Compute a summary value from a collection:

```yaml theme={null}
steps:
  - ordinal: 5
    description: "Calculate total"
    action:
      type: memory
    url: "https://app.example.com/products"
    riskLevel: low
    requiresConfirmation: false
    memoryOperations:
      - type: aggregate
        collection: prices
        operation: sum
        field: price
        outputVariable: totalPrice
```

| Field            | Type          | Required | Description                  |
| ---------------- | ------------- | :------: | ---------------------------- |
| `type`           | `"aggregate"` |    Yes   | Operation type               |
| `collection`     | string        |    Yes   | Source collection name       |
| `operation`      | AggregateOp   |    Yes   | Aggregation operation        |
| `field`          | string        |    No    | Field to aggregate on        |
| `outputVariable` | string        |    No    | Variable to store the result |

## Aggregate operations

| Operation      | Description               | Example result |
| -------------- | ------------------------- | -------------- |
| `sum`          | Sum of numeric values     | `1500`         |
| `count`        | Number of items           | `25`           |
| `avg`          | Average of numeric values | `60.5`         |
| `min`          | Minimum value             | `10`           |
| `max`          | Maximum value             | `200`          |
| `concat`       | Concatenate string values | `"A, B, C"`    |
| `unique_count` | Count of unique values    | `18`           |

## Complete example

Scrape a product listing across multiple pages and export to CSV:

```yaml theme={null}
title: Scrape product catalog
steps:
  - ordinal: 0
    description: "Navigate to product list"
    action:
      type: navigate
      url: "https://store.example.com/products"
    url: "https://store.example.com/products"
    riskLevel: low
    requiresConfirmation: false

  - ordinal: 1
    description: "Loop through products on current page"
    action:
      type: extract
      script: "JSON.stringify([...document.querySelectorAll('.product')].map(e => e.textContent))"
    url: "https://store.example.com/products"
    riskLevel: low
    requiresConfirmation: false
    loop:
      forEach: "collection:productElements"
      itemVariable: product
      maxIterations: 100
    steps:
      - ordinal: 0
        description: "Capture product name"
        action:
          type: extract
          script: "document.querySelector('.product-name').textContent"
        url: "https://store.example.com/products"
        riskLevel: low
        requiresConfirmation: false
        captures:
          - name: name
            strategy: snapshot
        memoryOperations:
          - type: append
            collection: products
            source: name

  - ordinal: 2
    description: "Count products"
    action:
      type: memory
    url: "https://store.example.com/products"
    riskLevel: low
    requiresConfirmation: false
    memoryOperations:
      - type: aggregate
        collection: products
        operation: count
        outputVariable: productCount

  - ordinal: 3
    description: "Export products to CSV"
    action:
      type: export
      exportCollection: products
      exportFormat: csv
      exportPath: "./output/products.csv"
    url: "https://store.example.com/products"
    riskLevel: low
    requiresConfirmation: false
```

## Iterating over collections

Use `collection:name` syntax in a `forEach` loop to iterate over collected items:

```yaml theme={null}
loop:
  forEach: "collection:products"
  itemVariable: product
```

See [Loops & Branches](/yaml/loops-and-branches) for loop details.