How to load data from Elasticsearch to MySQL Destination

Begin by analyzing the data structure in both Elasticsearch and MySQL. Ensure you comprehend the fields in your Elasticsearch index and how they map to columns in your MySQL tables. This will help you plan the data transformation process effectively.

Ensure that both Elasticsearch and MySQL are installed and running on your system. Install necessary command-line tools like `curl` for interacting with Elasticsearch, and ensure you have access to `mysql` command line or a similar MySQL client to execute SQL queries.

Use the Elasticsearch `_search` API to extract data. You can execute a curl command to retrieve the data in JSON format. For example:
```bash
curl -X GET "http://localhost:9200/your_index/_search?scroll=1m&size=1000" -H 'Content-Type: application/json' -d'
{
"query": {
"match_all": {}
}
}'
```
This command retrieves data from the specified index. Adjust the query parameters to suit your needs, such as filtering specific fields or applying conditions.

Write a script in a programming language like Python to read the JSON data and transform it into SQL insert statements. Use libraries such as `json` to parse the JSON data and format it for MySQL. For example:
```python
import json

def json_to_sql(json_data):
sql_statements = []
for record in json_data['hits']['hits']:
source = record['_source']
sql = f"INSERT INTO your_table (column1, column2) VALUES ('{source['field1']}', '{source['field2']}');"
sql_statements.append(sql)
return sql_statements
```

If your dataset is large, use Elasticsearch's scroll API to paginate through the data. Ensure your script handles the `scroll_id` and continues fetching data until all records are retrieved.

Execute the SQL insert statements using a MySQL client. You can use a script to automate this process. In Python, you might use a library like `mysql-connector-python`:
```python
import mysql.connector

connection = mysql.connector.connect(
host='localhost',
user='your_user',
password='your_password',
database='your_database'
)
cursor = connection.cursor()

sql_statements = json_to_sql(your_json_data)
for statement in sql_statements:
cursor.execute(statement)

connection.commit()
cursor.close()
connection.close()
```

Once the data transfer is complete, verify that the records in MySQL match those in Elasticsearch. Perform sample queries to check data integrity and consistency, ensuring all fields are accurately transferred and formatted.

This step-by-step guide will help you move data from Elasticsearch to MySQL without relying on third-party connectors or integrations.