datatable-gn

A Node.js implementation of a server-side processor for the jQuery DataTables plug-in.

The datatable-gn module provides backend query generation and result parsing to support DataTables server-side processing for SQL databases. This module does not connect to nor query databases, instead leaving those tasks to the calling application. SQL querying has been separated so that the caller can leverage his or her existing module choices for connection pools, database interfaces, and the like. This module has been used with node-mysql, sequelize, and strong-oracle.

An incomplete code example:

var async = require('async'),
    QueryBuilder = require('datatable-gn');

var tableDefinition = {
    sTableName: 'Orgs'
};

var queryBuilder = new QueryBuilder(tableDefinition);

// requestQuery is normally provided by the DataTables AJAX call
var requestQuery = {
    iDisplayStart: 0,
    iDisplayLength: 5
};

// Build an object of SQL statements
var queries = queryBuilder.buildQuery(requestQuery);

// Connect to the database
var myDbObject = ...;

// Execute the SQL statements generated by queryBuilder.buildQuery
myDbObject.query(queries.changeDatabaseOrSchema, function(err){
    if (err) { res.error(err); }
    else{
        async.parallel(
            {
                recordsFiltered: function(cb) {
                    myDbObject.query(queries.recordsFiltered, cb);
                },
                recordsTotal: function(cb) {
                    myDbObject.query(queries.recordsTotal, cb);
                },
                select: function(cb) {
                    myDbObject.query(queries.select, cb);
                }
            },
            function(err, results) {
                if (err) { res.error(err); }
                else {
                    res.json(queryBuilder.parseResponse(results));
                }
            }
        );
    }
});

API

The source code contains comments that may help you understand this module.

Constructor

Construct a QueryBuilder object.

Parameters

The datatable-gn constructor takes an object parameter containing the following properties. In the simplest case, only the first two options will be necessary.

• dbType - (Default: "mysql") The database language to use for queries ("mysql", "postgres", or "oracle"). The default value is mysql.

• sTableName - The name of the table in the database where a JOIN is not used. If a JOIN is used, set sSelectSql.

• sCountColumnName (Default: "id") The name of the column on which to do a SQL COUNT(). This is overridden with * when sSelectSql is set.

• sDatabaseOrSchema - If set, buildQuery will add a changeDatabaseOrSchema property to the object returned containing a USE sDatabaseOrSchema statement for MySQL / Postgres or an ALTER SESSION SET CURRENT_SCHEMA = sDatabaseOrSchema statement for Oracle.

• aSearchColumns - In database queries where JOIN is used, you may wish to specify an alternate array of column names that the search string will be applied against. Example:

aSearchColumns: ["table3.username", "table1.timestamp", "table1.urlType", "table1.mimeType", "table1.url", "table2.description"],

• sSelectSql - (Default: "id") A list of columns that will be selected. This can be used in combination with joins (see sFromSql).

• sFromSql - If set, this is used as the FROM clause of the SELECT statement. If not set, sTableName is used. Use this for more complex queries, for example when using JOIN. Example when using a double JOIN:

"table1 LEFT JOIN table2 ON table1.errorId=table2.errorId LEFT JOIN table3 ON table1.sessionId=table3.sessionId"

• sWhereAndSql - Use this to specify arbitrary SQL that you wish to append to the generated WHERE clauses with an AND condition.

• sDateColumnName - If this property and dateFrom and/or dateTo is set, a date range WHERE clause will be added to the SQL query. This should be set to the name of the datetime column that is to be used in the clause.

• dateFrom - If set, the query will return records greater than or equal to this date.

• dateTo - If set, the query will return records less than or equal to this date.

Returns

The query builder object.

Example:

var queryBuilder = new QueryBuilder({
    sTableName: 'user'
});

buildQuery

Builds an object containing the following properties:

changeDatabaseOrSchema: (Optional, if sDatabaseOrSchema is set) A USE sDatabaseOrSchema_ statement for MySQL / Postgres or an ALTER SESSION SET CURRENT_SCHEMA = sDatabaseOrSchema statement for Oracle.

recordsFiltered: (Optional, if requestQuery.search.value is set) A SELECT statement that counts the number of filtered entries in the database. This is used to calculate the recordsFiltered return value.

recordsTotal: A SELECT statement that counts the total number of unfiltered entries in the database. This is used to calculate the recordsTotal return value.

select: A SELECT statement that returns a page of filtered records from the database. This will use a LIMIT statement for MySQL / Postgres or a top-n query for Oracle.

Note that #2, #3, and #4 will include date filtering as well as any other filtering specified in sWhereAndSql.

Parameters

• requestQuery: An object containing the properties set by the client-side DataTables library as defined in sent parameters. Note that you may build your own requestQuery, omitting certain properties, and achieve a different outcome. For example, passing an empty requestQuery object will build a select statement that gets all rows from the table. Such a scenario could be useful for building a custom file export function.

Returns

The resultant object of query strings. The changeDatabaseOrSchema query should be executed first, and the others can be executed in sequence or (ideally) in parallel. Each database response should be collected into an object property having a key that matches the query object. The response object can later be passed to the parseReponse function.

Example:

var queries = queryBuilder.buildQuery(oRequestQuery);

parseResponse

Parses an object of responses that were received in response to each of the queries generated by buildQuery.

Parameters

• queryResult: The object of query responses.

Returns

An object containing the properties defined in returned data.

Example:

var result = queryBuilder.parseResponse(queryResponseObject);
res.json(result);

extractResponseVal

Extract a value from a database response. This is useful in situations where your database query returns a primitive value nested inside of an object inside of an array:

Parameters

• res: A database response.

Returns

The first enumerable object property of the first element in an array, or undefined

Example:

var val = queryBuilder.extractResponseVal([{COUNT(ID): 13}]);
console.log(val) //13

Database queries involving JOIN

Example using sSelectSql and sFromSql to create a JOIN query:

{
  sSelectSql: "table3.username,table1.timestamp,urlType,mimeType,table1.table3Id,url,table2.code,table2.description",
  sFromSql: "table1 LEFT JOIN table2 ON table1.errorId=table2.errorId LEFT JOIN table3 ON table1.sessionId=table3.sessionId",
}

Previous Contributors (Credits to them, I forked node-datatable)

• Matthew Hasbach
• Benjamin Flesch

TODO

1. Add an additional parameter to allow more then the requested number of records to be returned. This can be used to reduce the number of client-server calls (I think).
2. A more thorough SQL injection security review (volunteers?).
3. Unit tests (the original author is no longer working on the project that uses this module, so need volunteer)

References

1. Datatables Manual
2. How to Handle large datasets