rdbms2neo4j

///usr/bin/env jbang "$0" "$@" ; exit $?
//DEPS org.neo4j.driver:neo4j-java-driver:4.4.1
//DEPS org.postgresql:postgresql:42.2.24

// export JDBC_URL="jdbc:postgresql://db-examples.cmlvojdj5cci.us-east-1.rds.amazonaws.com/northwind?user=n4examples&password=36gdOVABr3Ex"
// export NEO4J_URL="neo4j+s://xxxx.databases.neo4j.io"
// export NEO4J_PASSWORD="secret"
// jbang rdbms2neo4j Customer

import static java.lang.System.*;
import java.sql.*;
import java.util.*;
import org.neo4j.driver.*;
import org.neo4j.driver.summary.*;

public class rdbms2neo4j {

    static final String INSERT_STATEMENT = "UNWIND $data AS row CREATE (n:`%s`) SET n = row";
    static final int BATCH_SIZE = 10000;

    public static void main(String... args) throws Exception {
        String table=args[0];
        String statement = String.format(INSERT_STATEMENT, table);
        int nodesCreated = 0;
        try (org.neo4j.driver.Driver driver = GraphDatabase.driver(getenv("NEO4J_URL"), 
                             AuthTokens.basic("neo4j",getenv("NEO4J_PASSWORD")));
             Session session = driver.session();
             Connection con=DriverManager.getConnection(getenv("JDBC_URL"));
             Statement stmt=con.createStatement();
             ResultSet rs=stmt.executeQuery("SELECT * FROM "+table)) {
                ResultSetMetaData meta=rs.getMetaData();
                String[] cols=new String[meta.getColumnCount()];
                for (int c=1;c<=cols.length;c++) 
                    cols[c-1]=meta.getColumnName(c);
                List<Map<String,Object>> data = new ArrayList<>();
                while (rs.next()) {
                    Map<String,Object> row=new HashMap<>(cols.length);
                    for (int c=1;c<=cols.length;c++) {
                        // todo unsupported datatypes like BigDecimal
                        row.put(cols[c-1], rs.getObject(c)); 
                    }
                    data.add(row);
                    if (data.size() == BATCH_SIZE) {
                        ResultSummary sum = session.writeTransaction(
                            tx -> tx.run(statement, Collections.singletonMap("data", data)).consume());
                        nodesCreated += sum.counters().nodesCreated();
                        data.clear();
                    }
                }
                if (!data.isEmpty()) {
                    ResultSummary sum = session.writeTransaction(tx -> 
                        tx.run(statement, Collections.singletonMap("data", data)).consume());
                    nodesCreated += sum.counters().nodesCreated();
                    out.println("Nodes created: " + nodesCreated);
                }
             }
    }
}