Batch Scripting in Nifi through Custom Groovy Script

I want to fetch the flowfiles from the input stream in bulk and create the one bulk insertion query for Clickhouse.

I am currently creating the the one insertion query for each document of mongoDB. Here is following code for this:

import groovy.json.JsonSlurper
import java.nio.charset.StandardCharsets
import org.apache.nifi.processor.io.StreamCallback
import org.apache.commons.io.IOUtils

class GenerateInsertQuery implements StreamCallback {

    // Convert MongoDB date string to ClickHouse-compatible DateTime format
    String toClickhouseDateFormat(String mongoDate) {
        if (!mongoDate) return null

        def parsedDate = null
        def formats = ["yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", "yyyy-MM-dd'T'HH:mm:ss'Z'"]

        formats.each { format ->
            try {
                parsedDate = Date.parse(format, mongoDate)
                return
            } catch (Exception e) {
            }
        }

        // If none of the formats match, return null
        return parsedDate != null ? parsedDate.format("yyyy-MM-dd HH:mm:ss") : null
    }

    // Sanitize value for SQL
    String sanitizeValue(String value) {
        if (value == null || value.trim().isEmpty() || value == '') return null
        return value.replace("'", "''")
    }

    @Override
    void process(InputStream inputStream, OutputStream outputStream) {
        // Read the JSON content from the FlowFile
        def json_content = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
        def json_object = new JsonSlurper().parseText(json_content)

        // Extract and sanitize values, using null-safe operator
        def id_value = sanitizeValue(json_object?._id?.'$oid')
        def first_name = sanitizeValue(json_object?.first_name)
        def last_name = sanitizeValue(json_object?.last_name)

        // Create the SQL INSERT query
        def insert_query = """INSERT INTO db.table_name (comma separated columns names)
                            VALUES (
                            ${id_value != null ? "'${id_value}'" : null},
                            ${first_name != null ? "'${first_name}'" : null},
                            ${last_name != null ? "'${last_name}'" : null}
                        );"""

        // Write the SQL query back to the FlowFile
        outputStream.write(insert_query.getBytes(StandardCharsets.UTF_8))
    }
}

// Apply the StreamCallback to modify the FlowFile content
flowFile = session.get()
if (flowFile) {
    try {
        flowFile = session.write(flowFile, new GenerateInsertQuery())
        session.transfer(flowFile, REL_SUCCESS)
    } catch (Exception e) {
        // Handle any errors by transferring to the failure relationship
        session.transfer(flowFile, REL_FAILURE)
    }
} else {
    session.transfer(flowFile, REL_FAILURE)
}

How can I make this script for nifi to make the bulk insertion query?. If anyone knows kindly create that script for me by modifying this script.