Querying with OQL
This section provides a high-level introduction to Geode querying such as building a query string and describes query language features.
Geode provides a SQL-like querying language that allows you to access data stored in Geode regions. Since Geode regions are key-value stores where values can range from simple byte arrays to complex nested objects, Geode uses a query syntax based on OQL (Object Query Language) to query region data. OQL and SQL have many syntactical similarities, however they have significant differences. For example, while OQL does not offer all of the capabilities of SQL like aggregates, OQL does allow you to execute queries on complex object graphs, query object attributes and invoke object methods.
The syntax of a typical Geode OQL query is:
[IMPORT package] SELECT [DISTINCT] projectionList FROM collection1, [collection2, …] [WHERE clause] [ORDER BY order_criteria [desc]]
Therefore, a simple Geode OQL query resembles the following:
SELECT DISTINCT * FROM /exampleRegion WHERE status = ‘active’
An important characteristic of Geode querying to note is that by default, Geode queries on the values of a region and not on keys. To obtain keys from a region, you must use the keySet path expression on the queried region. For example,
For those new to the Geode querying, see also the Geode Querying FAQ and Examples.
Advantages of OQL
The following list describes some of the advantages of using an OQL-based querying language:
- You can query on any arbitrary object
- You can navigate object collections
- You can invoke methods and access the behavior of objects
- Data mapping is supported
- You are not required to declare types. Since you do not need type definitions, you can work across multiple languages
- You are not constrained by a schema