# Dataset Entity

The Dataset entity represents collections of data with a common schema (tables, views, files, topics, etc.). This guide covers comprehensive dataset operations in SDK V2.

## Creating a Dataset

### Minimal Dataset

Only platform and name are required:

```java
Dataset dataset = Dataset.builder()
    .platform("snowflake")
    .name("my_database.my_schema.my_table")
    .build();
```

### With Environment

Specify environment (PROD, DEV, STAGING, etc.):

```java
Dataset dataset = Dataset.builder()
    .platform("snowflake")
    .name("my_table")
    .env("PROD")
    .build();
// URN: urn:li:dataset:(urn:li:dataPlatform:snowflake,my_table,PROD)
```

### With Metadata

Add description and display name at construction:

```java
Dataset dataset = Dataset.builder()
    .platform("bigquery")
    .name("project.dataset.table")
    .env("PROD")
    .description("User transactions table")
    .displayName("User Transactions")
    .build();
```

### With Custom Properties

Include custom properties in builder:

```java
Map<String, String> props = new HashMap<>();
props.put("team", "data-engineering");
props.put("retention", "90_days");

Dataset dataset = Dataset.builder()
    .platform("postgres")
    .name("public.users")
    .customProperties(props)
    .build();
```

### With Platform Instance

For multi-instance platforms:

```java
Dataset dataset = Dataset.builder()
    .platform("kafka")
    .name("user-events")
    .platformInstance("kafka-prod-cluster")
    .build();
```

## URN Construction

Dataset URNs follow the pattern:

```
urn:li:dataset:(urn:li:dataPlatform:{platform},{name},{env})
```

**Automatic URN creation:**

```java
Dataset dataset = Dataset.builder()
    .platform("snowflake")
    .name("analytics.public.events")
    .env("PROD")
    .build();

DatasetUrn urn = dataset.getDatasetUrn();
// urn:li:dataset:(urn:li:dataPlatform:snowflake,analytics.public.events,PROD)
```

## Description Operations

### Mode-Aware Description

The `setDescription()` method routes to different aspects based on mode:

```java
// SDK mode (default) - writes to editableDatasetProperties
dataset.setDescription("User-provided description");

// INGESTION mode - writes to datasetProperties
dataset.setDescription("Ingested from Snowflake");
```

### Explicit Aspect Targeting

Control which aspect to write:

```java
// System description (datasetProperties)
dataset.setSystemDescription("Generated by ETL pipeline");

// Editable description (editableDatasetProperties)
dataset.setEditableDescription("User override description");
```

### Reading Description

Get description (prefers editable over system):

```java
String description = dataset.getDescription();
// Returns editableDatasetProperties.description if set
// Otherwise returns datasetProperties.description
```

## Display Name Operations

Similar to description, display names are mode-aware:

```java
// Mode-aware (SDK → editable, INGESTION → system)
dataset.setDisplayName("User Events");

// Explicit aspect targeting
dataset.setSystemDisplayName("user_events_table");
dataset.setEditableDisplayName("User Events Table");

// Read display name (prefers editable)
String name = dataset.getDisplayName();
```

## Tags

### Adding Tags

```java
// Simple tag name (auto-prefixed)
dataset.addTag("pii");
// Creates: urn:li:tag:pii

// Full tag URN
dataset.addTag("urn:li:tag:analytics");
```

### Removing Tags

```java
dataset.removeTag("pii");
dataset.removeTag("urn:li:tag:analytics");
```

### Tag Chaining

```java
dataset.addTag("pii")
       .addTag("sensitive")
       .addTag("gdpr");
```

## Owners

### Adding Owners

```java
import com.linkedin.common.OwnershipType;

// Technical owner
dataset.addOwner(
    "urn:li:corpuser:john_doe",
    OwnershipType.TECHNICAL_OWNER
);

// Data steward
dataset.addOwner(
    "urn:li:corpuser:jane_smith",
    OwnershipType.DATA_STEWARD
);

// Business owner
dataset.addOwner(
    "urn:li:corpuser:alice",
    OwnershipType.BUSINESS_OWNER
);
```

### Removing Owners

```java
dataset.removeOwner("urn:li:corpuser:john_doe");
```

### Owner Types

Available ownership types:

- `TECHNICAL_OWNER` - Maintains the technical implementation
- `BUSINESS_OWNER` - Business stakeholder
- `DATA_STEWARD` - Manages data quality and compliance
- `DATAOWNER` - Generic data owner
- `DEVELOPER` - Software developer
- `PRODUCER` - Data producer
- `CONSUMER` - Data consumer
- `STAKEHOLDER` - Other stakeholder

## Glossary Terms

### Adding Terms

```java
dataset.addTerm("urn:li:glossaryTerm:CustomerData");
dataset.addTerm("urn:li:glossaryTerm:Classification.Confidential");
```

### Removing Terms

```java
dataset.removeTerm("urn:li:glossaryTerm:CustomerData");
```

### Term Chaining

```java
dataset.addTerm("urn:li:glossaryTerm:Customer Data")
       .addTerm("urn:li:glossaryTerm:PII")
       .addTerm("urn:li:glossaryTerm:GDPR");
```

## Domain

### Setting Domain

```java
dataset.setDomain("urn:li:domain:Marketing");
```

### Removing Domain

```java
// Remove a specific domain
dataset.removeDomain("urn:li:domain:Marketing");

// Or clear all domains
dataset.clearDomains();
```

## Custom Properties

### Adding Individual Properties

```java
dataset.addCustomProperty("team", "data-engineering");
dataset.addCustomProperty("retention_days", "90");
dataset.addCustomProperty("cost_center", "12345");
```

### Setting All Properties

Replace all custom properties:

```java
Map<String, String> properties = new HashMap<>();
properties.put("team", "data-engineering");
properties.put("retention", "90_days");
properties.put("classification", "internal");

dataset.setCustomProperties(properties);
```

### Removing Properties

```java
dataset.removeCustomProperty("retention_days");
```

## Schema

### Setting Schema Metadata

```java
import com.linkedin.schema.*;

SchemaMetadata schema = new SchemaMetadata();
// Configure schema...
dataset.setSchema(schema);
```

### Setting Schema Fields

```java
import com.linkedin.schema.*;

List<SchemaField> fields = new ArrayList<>();

// String field
SchemaField userIdField = new SchemaField();
userIdField.setFieldPath("user_id");
userIdField.setNativeDataType("VARCHAR(255)");
userIdField.setType(
    new SchemaFieldDataType().setType(SchemaFieldDataType.Type.create(new StringType())));
fields.add(userIdField);

// Numeric field
SchemaField amountField = new SchemaField();
amountField.setFieldPath("amount");
amountField.setNativeDataType("DECIMAL(10,2)");
amountField.setType(
    new SchemaFieldDataType().setType(SchemaFieldDataType.Type.create(new NumberType())));
fields.add(amountField);

dataset.setSchemaFields(fields);
```

## Complete Example

```java
import datahub.client.v2.DataHubClientV2;
import datahub.client.v2.entity.Dataset;
import com.linkedin.common.OwnershipType;
import java.io.IOException;
import java.util.concurrent.ExecutionException;

public class DatasetExample {
    public static void main(String[] args) {
        // Create client
        DataHubClientV2 client = DataHubClientV2.builder()
            .server("http://localhost:8080")
            .build();

        try {
            // Build dataset with all metadata
            Dataset dataset = Dataset.builder()
                .platform("snowflake")
                .name("analytics.public.user_events")
                .env("PROD")
                .description("User interaction events from web and mobile")
                .displayName("User Events")
                .build();

            // Add tags
            dataset.addTag("pii")
                   .addTag("analytics")
                   .addTag("gdpr");

            // Add owners
            dataset.addOwner("urn:li:corpuser:data_team", OwnershipType.TECHNICAL_OWNER)
                   .addOwner("urn:li:corpuser:product_team", OwnershipType.BUSINESS_OWNER);

            // Add glossary terms
            dataset.addTerm("urn:li:glossaryTerm:CustomerData")
                   .addTerm("urn:li:glossaryTerm:EventData");

            // Set domain
            dataset.setDomain("urn:li:domain:Analytics");

            // Add custom properties
            dataset.addCustomProperty("team", "data-engineering")
                   .addCustomProperty("retention_days", "365")
                   .addCustomProperty("refresh_schedule", "daily");

            // Upsert to DataHub
            client.entities().upsert(dataset);

            System.out.println("Successfully created dataset: " + dataset.getUrn());

        } catch (IOException | ExecutionException | InterruptedException e) {
            e.printStackTrace();
        } finally {
            try {
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
```

## Updating Existing Datasets

### Load and Modify

```java
// Load existing dataset
DatasetUrn urn = new DatasetUrn("snowflake", "my_table", "PROD");
Dataset dataset = client.entities().get(urn);

// Add new metadata (creates patches)
dataset.addTag("new-tag")
       .addOwner("urn:li:corpuser:new_owner", OwnershipType.TECHNICAL_OWNER);

// Apply patches
client.entities().update(dataset);
```

### Incremental Updates

```java
// Just add what you need
dataset.addTag("sensitive");
client.entities().update(dataset);

// Later, add more
dataset.addCustomProperty("updated_at", String.valueOf(System.currentTimeMillis()));
client.entities().update(dataset);
```

## Builder Options Reference

| Method                     | Required | Description                                   |
| -------------------------- | -------- | --------------------------------------------- |
| `platform(String)`         | ✅ Yes   | Data platform (e.g., "snowflake", "bigquery") |
| `name(String)`             | ✅ Yes   | Fully qualified dataset name                  |
| `env(String)`              | No       | Environment (PROD, DEV, etc.) Default: PROD   |
| `platformInstance(String)` | No       | Platform instance identifier                  |
| `description(String)`      | No       | Dataset description                           |
| `displayName(String)`      | No       | Display name shown in UI                      |
| `customProperties(Map)`    | No       | Map of custom key-value properties            |

## Mode-Aware vs Explicit Methods

| Operation    | Mode-Aware Method  | SDK Mode Aspect             | INGESTION Mode Aspect |
| ------------ | ------------------ | --------------------------- | --------------------- |
| Description  | `setDescription()` | `editableDatasetProperties` | `datasetProperties`   |
| Display Name | `setDisplayName()` | `editableDatasetProperties` | `datasetProperties`   |

**Explicit methods** (always available):

- `setSystemDescription()` / `setEditableDescription()`
- `setSystemDisplayName()` / `setEditableDisplayName()`

## Common Patterns

### Creating Multiple Datasets

```java
for (String tableName : tableNames) {
    Dataset dataset = Dataset.builder()
        .platform("postgres")
        .name("public." + tableName)
        .env("PROD")
        .build();

    dataset.addTag("auto-generated")
           .addCustomProperty("created_by", "sync_job");

    client.entities().upsert(dataset);
}
```

### Batch Metadata Addition

```java
Dataset dataset = Dataset.builder()
    .platform("snowflake")
    .name("my_table")
    .build();

List<String> tags = Arrays.asList("pii", "sensitive", "gdpr");
tags.forEach(dataset::addTag);

client.entities().upsert(dataset);  // Emits all tags in one call
```

### Conditional Metadata

```java
if (isPII(dataset)) {
    dataset.addTag("pii")
           .addTerm("urn:li:glossaryTerm:PersonalData");
}

if (requiresGovernance(dataset)) {
    dataset.addOwner("urn:li:corpuser:governance_team", OwnershipType.DATA_STEWARD);
}
```

## Next Steps

- **[Chart Entity](./chart-entity.md)** - Working with chart entities
- **[Patch Operations](./patch-operations.md)** - Deep dive into patches
- **[Migration Guide](./migration-from-v1.md)** - Upgrading from V1

## Examples

### Basic Dataset Creation

```java
{{ inline /metadata-integration/java/examples/src/main/java/io/datahubproject/examples/v2/DatasetCreateExample.java show_path_as_comment }}
```

### Dataset Patch Operations

```java
{{ inline /metadata-integration/java/examples/src/main/java/io/datahubproject/examples/v2/DatasetPatchExample.java show_path_as_comment }}
```

### Comprehensive Dataset Example

```java
{{ inline /metadata-integration/java/examples/src/main/java/io/datahubproject/examples/v2/DatasetFullExample.java show_path_as_comment }}
```