how to dynamically insert multiple rows into google cloud spanner - node.js

Question

In the below code snippet, Inserting multiple rows with static values. How do I insert multiple rows dynamically into the spanner database in one transaction?
function writeUsingDml(instanceId, databaseId, projectId) {
const {Spanner} = require('#google-cloud/spanner');
const spanner = new Spanner({
projectId: projectId,
});
const instance = spanner.instance(instanceId);
const database = instance.database(databaseId);
database.runTransaction(async (err, transaction) => {
if (err) {
console.error(err);
return;
}
try {
const rowCount = await transaction.runUpdate({
sql: `INSERT Singers (SingerId, FirstName, LastName) VALUES
(12, 'Melissa', 'Garcia'),
(13, 'Russell', 'Morales'),
(14, 'Jacqueline', 'Long'),
(15, 'Dylan', 'Shaw')`,
});
console.log(`${rowCount} records inserted.`);
await transaction.commit();
} catch (err) {
console.error('ERROR:', err);
} finally {
database.close();
}
});
}
For now, I am inserting a single row dynamically as follows and I want to extend this to multiple rows
var sqlString = "Insert " + tName
var cNames = "( "
var cValues = "( "
for(var col in cols) {
cNames = cNames + col + ", " ;
const cValue = cols[col];
if (typeof cValue == 'string' || cValue instanceof String){
cValues = cValues + "'" + cValue + "', "
}else{
cValues = cValues + cValue + ", ";
}
}
return sqlString + cNames + ") values " + cValues + ")";

Answer 1

If you want to insert many rows, it may be easier to use BatchTransaction.insert
https://cloud.google.com/nodejs/docs/reference/spanner/2.1.x/BatchTransaction#insert
database.runTransaction(async (err, transaction) => {
if (err) {
console.error(err);
return;
}
try {
var itemsToInsert = [
{ SingerId: 12, FirstName: 'Mellissa', LastName: 'Garcia' },
{ SingerId: 13, FirstName: 'Russell', LastName: 'Morales' },
{ SingerId: 14, FirstName: 'Jacqueline', LastName: 'Long' },
{ SingerId: 15, FirstName: 'Dylan', LastName: 'Shaw' },
]
transaction.insert('Singers', itemsToInsert);;
await transaction.commit();
console.log(`${itemsToInsert.length} records inserted.`);
} catch (err) {
console.error('ERROR:', err);
} finally {
database.close();
}
});
If you want to use DML though, you can make the SQL statement programatically. The following will build the insert statement. I didn't run your version, but I think it may have syntax errors related to trailing commas.
function buildSqlInsert(tableName, columnNames, rows) {
var sqlString = "INSERT " + tableName + " (" + columnNames.join(', ') + ") VALUES \n";
// add each row being careful to match the column order with columnNames
rows.forEach(row => {
sqlString += "(";
columnNames.forEach(columnName => {
var columnValue = row[columnName]
// strings should be quoted
if (typeof columnValue == 'string' || columnValue instanceof String) {
columnValue = "'" + columnValue + "'";
}
sqlString += columnValue + ", ";
});
// trim added chars.
sqlString = sqlString.substring(0, sqlString.length - 2);
sqlString += "),\n"
});
// trim added comma/newline
sqlString = sqlString.substring(0, sqlString.length - 2);
return sqlString
}
insertStatement = buildSqlInsert('Singers', Object.keys(itemsToInsert[0]), itemsToInsert)
const rowCount = await transaction.runUpdate({
sql: insertStatement,
});

Answer 2

You can also bind the rows you want to insert to an array-of-struct parameter and use that in an insert statement like follows:
INSERT INTO Singers(SingerId, FirstName, LastName)
SELECT * FROM UNNEST(#struct_array_param)
Where #struct_array_param is a bound parameter containing array of STRUCTS(tuples). In addition to being succinct and safer SQL syntax, using bound parameters offers the additional advantage of being able to use the same cached query plan for multiple executions of the same insert statement(with different bound values).