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

# getCatalogSchema

## getCatalogSchema

A function for retrieving and processing schema information from a Singer catalog for a specific stream. This function extracts the schema definition and ensures proper formatting for array types.

### Basic Usage

```typescript theme={null}
import * as gs from '@hotglue/gluestick-ts';

const schema = gs.getCatalogSchema("users");
console.log(schema.properties);
```

### Key Methods

***

## getCatalogSchema(stream: string): SingerHeaderMap

Retrieves the schema definition for a specific stream from the Singer catalog and processes it for proper formatting.

### Usage

```typescript theme={null}
// Get schema for a specific stream
const userSchema = gs.getCatalogSchema("users");

// Use schema with export functions
gs.toExport(df, "users", "./output", {
    exportFormat: 'singer',
    schema: userSchema
});
```

### Parameters

* `stream` (string): Name of the stream to get schema for (can be stream name or tap\_stream\_id)

### Returns

* `SingerHeaderMap`: Processed schema object with proper type definitions and array handling

### Schema Structure

The returned schema object has the following structure:

```typescript theme={null}
{
  type: ["object", "null"],
  properties: {
    // Stream properties with their types and definitions
  }
}
```

### Error Handling

The function throws errors in the following cases:

* **No catalog found**: When the catalog file cannot be read or doesn't exist
* **Stream not found**: When the specified stream doesn't exist in the catalog

```typescript theme={null}
try {
    const schema = gs.getCatalogSchema("nonexistent_stream");
} catch (error) {
    console.error(error.message);
    // "No schema found in catalog for stream nonexistent_stream"
}
```

## Common Patterns

### Get Schema for Multiple Streams

```typescript theme={null}
import * as gs from '@hotglue/gluestick-ts';

const reader = new gs.Reader();
const availableStreams = reader.keys();

const schemas = {};
for (const stream of availableStreams) {
    try {
        schemas[stream] = gs.getCatalogSchema(stream);
    } catch (error) {
        console.warn(`No schema found for ${stream}:`, error.message);
    }
}
```

### Notes

* Requires a valid Singer catalog file in the project directory
* The function accesses the catalog through the Reader class's private `readCatalog` method
* Array types are automatically normalized to include `items` properties
* The returned schema is compatible with Singer export formats
* Schema properties are preserved as-is from the original catalog