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Stop Merge

Stops and finalizes a merge operation, applying all accumulated values atomically to the database.

Common Properties​

  • Name - The custom name of the node.
  • Color - The custom color of the node.
  • Delay Before (sec) - Waits in seconds before executing the node.
  • Delay After (sec) - Waits in seconds after executing node.
  • Continue On Error - Automation will continue regardless of any error. The default value is false.
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If the ContinueOnError property is true, no error is caught when the project is executed, even if a Catch node is used.

Inputs​

  • Merge ID - The unique identifier of the merge operation to finalize, as returned by the Start Merge node.

How It Works​

The Stop Merge node finalizes a merge operation and applies all accumulated values atomically to the database.

When executed, the node:

  1. Validates the merge ID
  2. Retrieves the merge operator
  3. Applies all accumulated values atomically
  4. Updates the database with the final result
  5. Removes the merge operator from memory
  6. Releases all associated resources
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All values added via Merge nodes are applied together atomically when Stop Merge is called.

Examples​

Example 1: Basic Counter​

Complete a counter increment:

1. Start Merge
   Database Id: {{db_id}}
   Key: page_views
   Operation Type: Increment
   → merge_id

2. Merge
   Merge Id: {{merge_id}}
   Value: 1

3. Stop Merge
   Merge Id: {{merge_id}}

4. Get Result
   Database Id: {{db_id}}
   Key: page_views
   → total_views

Log "Total views: {{total_views}}"

Example 2: Inventory Decrement with Validation​

Decrease inventory and verify:

1. Start Merge
   Database Id: {{db_id}}
   Key: product:SKU123:stock
   Operation Type: Decrement
   → merge_id

2. For each order_item in {{order}}:
   Merge
     Merge Id: {{merge_id}}
     Value: {{order_item.quantity}}

3. Stop Merge
   Merge Id: {{merge_id}}

4. Get Final Stock
   Database Id: {{db_id}}
   Key: product:SKU123:stock
   → final_stock

5. If {{final_stock}} < 0:
   Alert "Stock went negative!"

Example 3: JSON Merge with Result Check​

Merge configuration and verify:

1. Start Merge
   Database Id: {{db_id}}
   Key: app:config
   Operation Type: JSON
   → merge_id

2. Merge (defaults)
   Merge Id: {{merge_id}}
   Value: {"theme": "light", "language": "en"}

3. Merge (overrides)
   Merge Id: {{merge_id}}
   Value: {"theme": "dark"}

4. Stop Merge
   Merge Id: {{merge_id}}

5. Get Configuration
   Database Id: {{db_id}}
   Key: app:config
   → config

Log "Final config: {{config}}"
(Result: {"theme": "dark", "language": "en"})

Example 4: Analytics Collection​

Collect and finalize analytics:

1. Start Merge
   Database Id: {{db_id}}
   Key: analytics:daily:{{date}}
   Operation Type: Increment
   → merge_id

2. For each hour in day:
   Get Hourly Count
     → hourly_count
   Merge
     Merge Id: {{merge_id}}
     Value: {{hourly_count}}

3. Stop Merge
   Merge Id: {{merge_id}}

4. Get Daily Total
   Database Id: {{db_id}}
   Key: analytics:daily:{{date}}
   → daily_total

Log "Daily total: {{daily_total}} events"

Example 5: Error Handling​

Handle merge completion with error handling:

Try:
  1. Start Merge
     Database Id: {{db_id}}
     Key: stats:total
     Operation Type: Increment
     → merge_id

  2. For each value in {{values}}:
     Merge
       Merge Id: {{merge_id}}
       Value: {{value}}

  3. Stop Merge
     Merge Id: {{merge_id}}

  Log "Merge completed successfully"

Catch:
  Log "Merge failed: {{error}}"

Tips for Effective Use​

  • Always Call Stop Merge - Every Start Merge should have a Stop Merge
  • Verify Results - Use Get after Stop Merge to verify the final value
  • Handle Errors - Use try-catch to handle stop merge errors
  • Immediate Effect - Changes are applied immediately when Stop Merge executes
  • One Stop Per Merge - Each merge operation should be stopped only once
  • Check Final Values - Especially important for decrement operations

Common Errors and Solutions​

Error: "merge id cannot be empty"​

Solution: Ensure you're passing the merge ID from Start Merge.

Correct:
  Start Merge → merge_id
  Merge operations...
  Stop Merge (Merge ID: {{merge_id}})

Error: Merge Operator Not Found​

Solution: The merge operation doesn't exist. Ensure:

  • Start Merge was successful
  • Merge ID is correct
  • Merge operation wasn't already stopped
  • No errors occurred during Start Merge
Verify flow:
  1. Start Merge → Check success → merge_id
  2. Merge operations
  3. Stop Merge (once only)

Error: Database Write Error​

Solution: The database couldn't be updated. Check:

  • Database is still open
  • Disk space is available
  • No concurrent access conflicts
  • Database isn't corrupted

What Happens When Stop Merge is Called​

For Increment Operations​

  1. All merged values are summed
  2. Sum is added to current value in database
  3. Result stored atomically
  4. Example: Current=10, Merged(5+3+2)=10, Result=20

For Decrement Operations​

  1. All merged values are summed
  2. Sum is subtracted from current value
  3. Result stored atomically
  4. Example: Current=100, Merged(10+20)=30, Result=70

For JSON Operations​

  1. All merged objects are combined
  2. Later values override earlier ones
  3. Final merged object stored
  4. Example: {a:1} + {b:2} + {a:3} = {a:3, b:2}

Auto-Finalization​

If Stop Merge is not called:

  • Merge operator is automatically finalized when the flow ends
  • Changes are applied automatically
  • No values are lost
  • Best practice: Always explicitly call Stop Merge

Performance Considerations​

  • Atomic Operation - All values applied in one atomic write
  • Efficient - More efficient than multiple individual updates
  • Disk Sync - Changes synced to disk for durability
  • Memory Release - Merge operator removed from memory
  • Immediate Visibility - Changes visible immediately after Stop Merge

Best Practices​

  • Explicit Stop - Always explicitly call Stop Merge for clarity
  • Verify Results - Use Get to check the final value
  • Error Handling - Wrap Stop Merge in try-catch
  • One Stop Only - Don't call Stop Merge multiple times for same merge ID
  • Document Purpose - Comment what the merge operation achieved
  • Check Constraints - Verify final values meet business rules

Merge Lifecycle​

Complete Lifecycle​

Start Merge → Accumulate Values (Merge) → Stop Merge → Value Applied

With Verification​

Start Merge → Merge → Merge → Stop Merge → Get → Verify Result

With Error Handling​

Try:
  Start Merge → Merge → Stop Merge
Catch:
  Handle Error

Use Cases​

Use Case 1: Page View Counter​

Start Merge (Increment)
  Key: page:{{page_id}}:views
Merge (Value: 1)
Stop Merge

Use Case 2: Bulk Inventory Update​

Start Merge (Decrement)
  Key: product:{{sku}}:stock
For each sold_item:
  Merge (Value: sold_item.quantity)
Stop Merge
Get stock → verify_not_negative

Use Case 3: Configuration Assembly​

Start Merge (JSON)
  Key: config:app
Merge (Value: base_config)
Merge (Value: env_config)
Merge (Value: user_config)
Stop Merge
Get config → active_config

Use Case 4: Statistics Rollup​

Start Merge (Increment)
  Key: stats:monthly:{{month}}
For each day:
  Get daily_stat
  Merge (Value: daily_stat)
Stop Merge

Use Case 5: Feature Metadata​

Start Merge (JSON)
  Key: feature:{{feature_id}}:metadata
Merge (Value: {created: timestamp})
Merge (Value: {author: user_id})
Merge (Value: {status: "active"})
Stop Merge

Verification Patterns​

Pattern 1: Basic Verification​

Stop Merge
Get key → result
If result != expected:
  Alert "Unexpected result"

Pattern 2: Constraint Checking​

Stop Merge
Get key → value
If value < 0:
  Log "Warning: Negative value"

Pattern 3: Audit Trail​

Stop Merge
Get key → new_value
Log "Value changed to {{new_value}}"
Create Audit Record

Atomicity Guarantee​

When Stop Merge executes:

  • All accumulated values are applied together
  • Either all succeed or all fail
  • No partial updates
  • Database remains consistent

Example:

Current value: 100
Merge operations: +10, +20, +30
Stop Merge: Value becomes 160 atomically
(Not 110, then 130, then 160)
  • Start Merge - Starts the merge operation
  • Merge - Adds values to the merge operation
  • Get - Retrieves the final merged value
  • Set - Alternative for simple value updates