Implementation:Apache Druid ModuleState

Knowledge Sources	Apache_Druid
Domains	Web_Console, Explore_View
Last Updated	2026-02-10 10:00 GMT

Overview

An immutable value class representing the complete state of an explore view module, including its identifier, filter expression, parameter values, and UI visibility flags.

Description

The ModuleState class encapsulates the configuration state of an explore view visualization module (e.g., time-chart, grouping-table, pie-chart, record-table). It stores the `moduleId`, a `moduleWhere` filter expression (defaulting to TRUE), a `parameterValues` dictionary, and boolean flags for `showModuleWhere` and `showControls`. The class provides immutable change methods, JSON serialization/deserialization via `fromJS` and `valueOf`, column rename propagation via `applyRename`, restriction to a query source via `restrictToQuerySource`, and smart column-to-module mapping via `applyShowColumn` and `applyShowMeasure`. A static `INIT_STATE` is initialized with the 'record-table' module.

Usage

Used as the primary state model for the explore view, persisted to localStorage, and updated by user interactions with module selectors, filter editors, and parameter controls.

Code Reference

Source Location

• Repository: Apache Druid
• File: web-console/src/views/explore-view/models/module-state.ts
• Lines: 1-184

Signature

export class ModuleState {
  static INIT_STATE: ModuleState;
  static fromJS(js: any): ModuleState;

  public readonly moduleId: string;
  public readonly moduleWhere: SqlExpression;
  public readonly parameterValues: ParameterValues;
  public readonly showModuleWhere: boolean;
  public readonly showControls: boolean;

  constructor(value: ModuleStateValue);
  valueOf(): ModuleStateValue;
  change(newValues: Partial<ModuleStateValue>): ModuleState;
  changeModuleWhere(moduleWhere: SqlExpression): ModuleState;
  changeParameterValues(parameterValues: ParameterValues): ModuleState;
  applyRename(rename: Rename): ModuleState;
  restrictToQuerySource(querySource: QuerySource, where: SqlExpression): ModuleState;
  applyShowColumn(column: Column): ModuleState;
  applyShowMeasure(measure: Measure): ModuleState;
}

Import

import { ModuleState } from '../models/module-state';

I/O Contract

Inputs

Name	Type	Required	Description
value / js	ModuleStateValue	Yes	Object containing moduleId, optional moduleWhere, parameterValues, and UI flags
moduleWhere	SqlExpression	Yes	A SQL filter expression scoped to the module
parameterValues	ParameterValues	Yes	A dictionary of parameter name to value for the module's parameters
rename	Rename (Map<string, string>)	Yes	A column rename mapping to propagate through parameter values
querySource	QuerySource	Yes	The current query source to restrict filters and parameters against
column	Column	Yes	A column to visualize, triggering automatic module selection
measure	Measure	Yes	A measure to add to the current or a new module

Outputs

Name	Type	Description
(return)	ModuleState	A new ModuleState instance reflecting the requested changes
(return)	ModuleStateValue	A serializable plain object representation (valueOf)

Usage Examples

Create initial state and change module

import { ModuleState } from '../models/module-state';

const state = ModuleState.INIT_STATE;
// state.moduleId === 'record-table'

const newState = state.change({ moduleId: 'time-chart' });
// newState.moduleId === 'time-chart'

Apply show column to auto-select module

const column = { name: '__time', sqlType: 'TIMESTAMP', nativeType: 'LONG' };
const chartState = state.applyShowColumn(column);
// chartState.moduleId === 'time-chart'

Deserialize from localStorage

import { ModuleState } from '../models/module-state';

const saved = JSON.parse(localStorage.getItem('explore-state'));
const state = ModuleState.fromJS(saved);

Related Pages

• Environment:Apache_Druid_Web_Console_Development