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IoT SQL

In AWS IoT, rules are defined using an SQL-like syntax. SQL statements are composed of three types of clauses:

  • SELECT - Required. Extracts information from the incoming payload and performs transformations.
  • FROM - Required. The MQTT topic filter from which the rule receives messages.
  • WHERE - Optional. Adds conditional logic that determines if a rule is evaluated and its actions are executed.

iotSql folder consists of methods for parsing SQL statements, applying transformations to incoming payload and executing additional actions.
There are methods for each step of the process.

  • Methods for parsing SQL statement:

    • parseSql.js - split up SQL statement to select, from and where parts
    • whereParser.js - tokenize WHERE part of SQL statement

  • Methods for applying transformations to incoming payload using previously parsed SQL:

    • applySqlWhere.js - build and apply where clause condition based on payload. This condition determines whether lambda function will execute or not.
    • applySqlSelect.js - builds event for lambda function.
    • sqlFunctions.js - local implementation of AWS Iot SQL functions
    • eval.js - executes select statement in context of SQL functions.

  • Methods for executing actions:

    • applyActions.js - execute additional action defined on Iot rule.