DbQueryEventNode - TypeScript

Introduction

DbQueryEventNode is a TypeScript library used to build database query execution trees. It can be used for query optimization, query tracing, and any other use case that requires a detailed execution history of a database query.

The library constructs a tree of events that correspond to each step of query execution. Each event contains information about the executed SQL statement, execution time, and any error that occurred during execution. The tree structure allows for easy navigation through the execution history and provides a detailed view of what happened during the query execution.

Installation

To install DbQueryEventNode, run the following command:

npm install db-query-event-node --save

Getting started

To start using DbQueryEventNode, you need to create a query execution tree and register event handlers. Here's an example:

import { ExecutionTree, EventTypes } from 'db-query-event-node';

const tree = new ExecutionTree();

tree.on(EventTypes.SqlStatement, event => {
    console.log('Executing SQL:', event.sql);
});

tree.on(EventTypes.ExecutionError, event => {
    console.error('Execution error:', event.error);
});

tree.start();

const result = await executeQuery('SELECT * FROM employees');

tree.end();

In this example, we create a new execution tree, register handlers for the SqlStatement and ExecutionError events, start the tree, execute a query, and end the tree. During the query execution, the registered handlers are called for each corresponding event.

API

The DbQueryEventNode API includes the following classes:

ExecutionTree

Represents the execution tree for a single database query.

Methods

• start(): void: Starts the execution tree.
• end(): void: Ends the execution tree.
• getCurrentNode(): EventNode: Returns the current event node in the execution tree.

Events

• SqlStatement: Event triggered when an SQL statement is executed.
• ExecutionStarted: Event triggered when query execution starts.
• ExecutionEnded: Event triggered when query execution ends.
• ExecutionError: Event triggered when an error occurs during query execution.

EventNode

Represents a node in the execution tree.

Properties

• eventType: string: The type of the event.
• sql: string: The SQL statement being executed.
• startTime: Date: The time when execution started.
• endTime: Date: The time when execution ended.
• error: Error: Any error that occurred during execution.
• parent: EventNode: The parent node in the execution tree.
• children: EventNode[]: The child nodes in the execution tree.

Conclusion

DbQueryEventNode is a powerful tool for building database query execution trees. It can be used to optimize queries, trace query execution, and diagnose query performance issues. Its simple API and rich features make it a must-have tool for any serious database developer.