Partial updates in Elasticsearch - Step-by-Step Execution

Concept Flow - Partial updates

Start with existing document

↓

Receive partial update data

↓

Merge partial data with existing document

↓

Save updated document

↓

End

Partial updates take new data and merge it into an existing document, then save the updated document.

Execution Sample

Elasticsearch

POST /my_index/_update/1
{
  "doc": {
    "age": 30
  }
}

This request updates the document with ID 1 by changing only the 'age' field to 30.

Execution Table

Step	Action	Input Data	Existing Document	Resulting Document
1	Start with existing document	N/A	{"name": "Alice", "age": 25, "city": "NY"}	{"name": "Alice", "age": 25, "city": "NY"}
2	Receive partial update	{"age": 30}	{"name": "Alice", "age": 25, "city": "NY"}	N/A
3	Merge partial update	{"age": 30}	{"name": "Alice", "age": 25, "city": "NY"}	{"name": "Alice", "age": 30, "city": "NY"}
4	Save updated document	N/A	{"name": "Alice", "age": 30, "city": "NY"}	{"name": "Alice", "age": 30, "city": "NY"}
5	End	N/A	N/A	N/A

💡 Partial update applied and document saved successfully.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
existing_document	{"name": "Alice", "age": 25, "city": "NY"}	{"name": "Alice", "age": 25, "city": "NY"}	{"name": "Alice", "age": 30, "city": "NY"}	{"name": "Alice", "age": 30, "city": "NY"}
partial_update	N/A	{"age": 30}	{"age": 30}	{"age": 30}
resulting_document	N/A	N/A	{"name": "Alice", "age": 30, "city": "NY"}	{"name": "Alice", "age": 30, "city": "NY"}

Key Moments - 2 Insights

Why does the partial update only change the 'age' field and not remove other fields?

Because the update merges the new data into the existing document, it only changes specified fields and keeps others intact, as shown in step 3 of the execution_table.

What happens if the partial update includes a new field not in the original document?

The new field is added to the document during the merge step, just like the 'age' field was updated, extending the document without removing existing fields.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the value of 'age' in the resulting document?

A 30

B 25

C null

D Not present

💡 Hint

Check the 'Resulting Document' column at step 3 in the execution_table.

At which step does the document get saved with the updated data?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Look for the 'Save updated document' action in the execution_table.

If the partial update included a new field 'email', when would it appear in the document?

A After step 1

B After step 2

C After step 3

D Never

💡 Hint

New fields appear after merging partial update, see step 3 in execution_table.

Concept Snapshot

Partial updates in Elasticsearch:
Use POST /index/_update/id with {"doc": {...}}.
Only specified fields change; others stay the same.
Merges new data into existing document.
Saves updated document automatically.

Full Transcript

Partial updates in Elasticsearch let you change only some fields of a document without replacing the whole document. The process starts with the existing document. Then, Elasticsearch receives the partial update data. It merges this data into the existing document, changing or adding only the specified fields. Finally, it saves the updated document. For example, updating the 'age' field from 25 to 30 keeps other fields like 'name' and 'city' unchanged. This merging behavior ensures efficient updates without losing data.