[maps] remove IVectorSource.getFieldNames (#159747)

`IVectorSource` interface has many similar sounding methods that are
used for different purposes. These lead to confusion and an unclear API
* getFieldNames
* getFields
* getFieldByName

Although `getFieldNames` sounds similar to `getFields`, the 2 are used
for very different purposes.
* getFieldNames returns a string array that is used to trigger source
re-fetch
* getFields returns an array of fields to drive UI such as field
selection for data driven styling

`getFieldNames` overlaps 100% in functionality with `getSyncMeta` and is
not needed. Combining output of `getFieldNames` into `getSyncMeta`
simplifies the `IVectorSource` API and removes some confusion.

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

x-pack/examples/third_party_maps_source_example/public/classes/custom_raster_source.tsx

@@ -106,10 +106,6 @@ export class CustomRasterSource implements IRasterSource {
     return false;
   }
 
-  getFieldNames(): string[] {
-    return [];
-  }
-
   renderSourceSettingsEditor(sourceEditorArgs: SourceEditorArgs): ReactElement<any> | null {
     return null;
   }

x-pack/plugins/maps/common/descriptor_types/data_request_descriptor_types.ts

@@ -46,6 +46,9 @@ export type SourceRequestMeta = DataFilters & {
 };
 
 export type VectorSourceRequestMeta = SourceRequestMeta & {
+  /*
+   * List of feature property keys used in client for data driven styling, join keys, and feature masking
+   */
   fieldNames: string[];
   timesliceMaskField?: string;
   sourceMeta: object | null;

x-pack/plugins/maps/public/classes/layers/heatmap_layer/heatmap_layer.ts

@@ -100,7 +100,7 @@ export class HeatmapLayer extends AbstractLayer {
       prevDataRequest: this.getSourceDataRequest(),
       requestMeta: buildVectorRequestMeta(
         this.getSource(),
-        this.getSource().getFieldNames(),
+        [], // fieldNames is empty because heatmap layer only support metrics
         syncContext.dataFilters,
         this.getQuery(),
         syncContext.isForceRefresh,

x-pack/plugins/maps/public/classes/layers/vector_layer/vector_layer.tsx

@@ -51,6 +51,7 @@ import {
 import { IVectorSource } from '../../sources/vector_source';
 import { LayerIcon, ILayer } from '../layer';
 import { InnerJoin } from '../../joins/inner_join';
+import { isSpatialJoin } from '../../joins/is_spatial_join';
 import { IField } from '../../fields/field';
 import { DataRequestContext } from '../../../actions';
 import { ITooltipProperty } from '../../tooltips/tooltip_property';
@@ -354,9 +355,12 @@ export class AbstractVectorLayer extends AbstractLayer implements IVectorLayer {
     isFeatureEditorOpenForLayer: boolean
   ): Promise<VectorSourceRequestMeta> {
     const fieldNames = [
-      ...source.getFieldNames(),
       ...style.getSourceFieldNames(),
-      ...this.getValidJoins().map((join) => join.getLeftField().getName()),
+      ...this.getValidJoins()
+        .filter((join) => {
+          return !isSpatialJoin(join.toDescriptor());
+        })
+        .map((join) => join.getLeftField().getName()),
     ];
 
     const timesliceMaskFieldName = await source.getTimesliceMaskFieldName();
@@ -550,7 +554,7 @@ export class AbstractVectorLayer extends AbstractLayer implements IVectorLayer {
 
     const joinRequestMeta = buildVectorRequestMeta(
       joinSource,
-      joinSource.getFieldNames(),
+      [], // fieldNames is empty because join sources only support metrics
       dataFilters,
       joinSource.getWhereQuery(),
       isForceRefresh,

x-pack/plugins/maps/public/classes/sources/es_agg_source/es_agg_source.ts

@@ -8,12 +8,16 @@
 import { i18n } from '@kbn/i18n';
 import { GeoJsonProperties } from 'geojson';
 import { DataView } from '@kbn/data-plugin/common';
-import type { IESAggSource } from './types';
+import type { IESAggSource, ESAggsSourceSyncMeta } from './types';
 import { AbstractESSource } from '../es_source';
 import { esAggFieldsFactory, IESAggField } from '../../fields/agg';
 import { AGG_TYPE, FIELD_ORIGIN } from '../../../../common/constants';
 import { getSourceAggKey } from '../../../../common/get_agg_key';
-import { AbstractESAggSourceDescriptor, AggDescriptor } from '../../../../common/descriptor_types';
+import {
+  AbstractESAggSourceDescriptor,
+  AggDescriptor,
+  DataFilters,
+} from '../../../../common/descriptor_types';
 import { IField } from '../../fields/field';
 import { ITooltipProperty } from '../../tooltips/tooltip_property';
 import { getAggDisplayName } from './get_agg_display_name';
@@ -142,6 +146,23 @@ export abstract class AbstractESAggSource extends AbstractESSource implements IE
     return false;
   }
 
+  /*
+   * Changes in requestMeta.fieldNames does not require re-fetch.
+   * It is not possible to filter metrics from responses so all metrics are always returned in all responses.
+   */
+  isFieldAware(): boolean {
+    return false;
+  }
+
+  /*
+   * Force re-fetch when requested metrics change.
+   */
+  getSyncMeta(dataFilters: DataFilters): ESAggsSourceSyncMeta {
+    return {
+      metrics: this.getMetricFields().map((esAggMetricField) => esAggMetricField.getName()),
+    };
+  }
+
   getGeoGridPrecision(zoom: number): number {
     return 0;
   }

x-pack/plugins/maps/public/classes/sources/es_agg_source/index.ts

@@ -5,6 +5,6 @@
  * 2.0.
  */
 
-export type { IESAggSource } from './types';
+export type { IESAggSource, ESAggsSourceSyncMeta } from './types';
 export { AbstractESAggSource, DEFAULT_METRIC } from './es_agg_source';
 export { getAggDisplayName } from './get_agg_display_name';

x-pack/plugins/maps/public/classes/sources/es_agg_source/types.ts

@@ -25,3 +25,7 @@ export interface IESAggSource extends IESSource {
   isGeoGridPrecisionAware(): boolean;
   getGeoGridPrecision(zoom: number): number;
 }
+
+export interface ESAggsSourceSyncMeta {
+  metrics: string[];
+}

x-pack/plugins/maps/public/classes/sources/es_geo_grid_source/es_geo_grid_source.tsx

@@ -35,7 +35,7 @@ import {
 } from '../../../../common/constants';
 import { getDataSourceLabel, getDataViewLabel } from '../../../../common/i18n_getters';
 import { buildGeoGridFilter } from '../../../../common/elasticsearch_util';
-import { AbstractESAggSource } from '../es_agg_source';
+import { AbstractESAggSource, ESAggsSourceSyncMeta } from '../es_agg_source';
 import { DataRequestAbortError } from '../../util/data_request';
 import { LICENSED_FEATURES } from '../../../licensed_features';
 
@@ -56,11 +56,10 @@ import { isMvt } from './is_mvt';
 import { VectorStyle } from '../../styles/vector/vector_style';
 import { getIconSize } from './get_icon_size';
 
-interface ESGeoGridSourceSyncMeta {
-  geogridPrecision: number;
-  requestType: RENDER_AS;
-  resolution: GRID_RESOLUTION;
-}
+type ESGeoGridSourceSyncMeta = ESAggsSourceSyncMeta &
+  Pick<ESGeoGridSourceDescriptor, 'requestType' | 'resolution'> & {
+    geogridPrecision: number;
+  };
 
 const MAX_GEOTILE_LEVEL = 29;
 
@@ -160,6 +159,7 @@ export class ESGeoGridSource extends AbstractESAggSource implements IMvtVectorSo
 
   getSyncMeta(dataFilters: DataFilters): ESGeoGridSourceSyncMeta {
     return {
+      ...super.getSyncMeta(dataFilters),
       geogridPrecision: this.getGeoGridPrecision(dataFilters.zoom),
       requestType: this._descriptor.requestType,
       resolution: this._descriptor.resolution,
@@ -189,10 +189,6 @@ export class ESGeoGridSource extends AbstractESAggSource implements IMvtVectorSo
     return isMvt(this._descriptor.requestType, this._descriptor.resolution);
   }
 
-  getFieldNames() {
-    return this.getMetricFields().map((esAggMetricField) => esAggMetricField.getName());
-  }
-
   isGeoGridPrecisionAware(): boolean {
     if (this.isMvt()) {
       // MVT gridded data should not bootstrap each time the precision changes

x-pack/plugins/maps/public/classes/sources/es_geo_line_source/es_geo_line_source.tsx

@@ -20,12 +20,13 @@ import {
 } from '../../../../common/constants';
 import { getField, addFieldToDSL } from '../../../../common/elasticsearch_util';
 import {
+  DataFilters,
   ESGeoLineSourceDescriptor,
   ESGeoLineSourceResponseMeta,
   VectorSourceRequestMeta,
 } from '../../../../common/descriptor_types';
 import { getDataSourceLabel, getDataViewLabel } from '../../../../common/i18n_getters';
-import { AbstractESAggSource } from '../es_agg_source';
+import { AbstractESAggSource, ESAggsSourceSyncMeta } from '../es_agg_source';
 import { DataRequest } from '../../util/data_request';
 import { convertToGeoJson } from './convert_to_geojson';
 import { ESDocField } from '../../fields/es_doc_field';
@@ -39,7 +40,8 @@ import { getIsGoldPlus } from '../../../licensed_features';
 import { LICENSED_FEATURES } from '../../../licensed_features';
 import { mergeExecutionContext } from '../execution_context_utils';
 
-type ESGeoLineSourceSyncMeta = Pick<ESGeoLineSourceDescriptor, 'splitField' | 'sortField'>;
+type ESGeoLineSourceSyncMeta = ESAggsSourceSyncMeta &
+  Pick<ESGeoLineSourceDescriptor, 'splitField' | 'sortField'>;
 
 const MAX_TRACKS = 250;
 
@@ -107,8 +109,9 @@ export class ESGeoLineSource extends AbstractESAggSource {
     );
   }
 
-  getSyncMeta(): ESGeoLineSourceSyncMeta {
+  getSyncMeta(dataFilters: DataFilters): ESGeoLineSourceSyncMeta {
     return {
+      ...super.getSyncMeta(dataFilters),
       splitField: this._descriptor.splitField,
       sortField: this._descriptor.sortField,
     };
@@ -141,14 +144,6 @@ export class ESGeoLineSource extends AbstractESAggSource {
     });
   }
 
-  getFieldNames() {
-    return [
-      ...this.getMetricFields().map((esAggMetricField) => esAggMetricField.getName()),
-      this._descriptor.splitField,
-      this._descriptor.sortField,
-    ];
-  }
-
   async getFields(): Promise<IField[]> {
     return [...this.getMetricFields(), this._createSplitField()];
   }

x-pack/plugins/maps/public/classes/sources/es_pew_pew_source/es_pew_pew_source.tsx

@@ -93,6 +93,7 @@ export class ESPewPewSource extends AbstractESAggSource {
 
   getSyncMeta(dataFilters: DataFilters) {
     return {
+      ...super.getSyncMeta(dataFilters),
       geogridPrecision: this.getGeoGridPrecision(dataFilters.zoom),
     };
   }

x-pack/plugins/maps/public/classes/sources/es_search_source/es_search_source.tsx

@@ -78,6 +78,7 @@ import { FeatureGeometryFilterForm } from '../../../connected_components/mb_map/
 
 type ESSearchSourceSyncMeta = Pick<
   ESSearchSourceDescriptor,
+  | 'geoField'
   | 'filterByMapBounds'
   | 'sortField'
   | 'sortOrder'
@@ -211,10 +212,6 @@ export class ESSearchSource extends AbstractESSource implements IMvtVectorSource
     }
   }
 
-  getFieldNames(): string[] {
-    return [this._descriptor.geoField];
-  }
-
   isMvt() {
     return this._descriptor.scalingType === SCALING_TYPES.MVT;
   }
@@ -282,12 +279,9 @@ export class ESSearchSource extends AbstractESSource implements IMvtVectorSource
 
     const indexPattern: DataView = await this.getIndexPattern();
 
-    const fieldNames = requestMeta.fieldNames.filter(
-      (fieldName) => fieldName !== this._descriptor.geoField
-    );
     const { docValueFields, sourceOnlyFields, scriptFields } = getDocValueAndSourceFields(
       indexPattern,
-      fieldNames,
+      requestMeta.fieldNames,
       'epoch_millis'
     );
     const topHits: {
@@ -398,7 +392,6 @@ export class ESSearchSource extends AbstractESSource implements IMvtVectorSource
     };
   }
 
-  // requestMeta.fieldNames contains geo field and any fields needed for styling features
   // Performs Elasticsearch search request being careful to pull back only required fields to minimize response size
   async _getSearchHits(
     layerName: string,
@@ -408,12 +401,9 @@ export class ESSearchSource extends AbstractESSource implements IMvtVectorSource
   ) {
     const indexPattern = await this.getIndexPattern();
 
-    const fieldNames = requestMeta.fieldNames.filter(
-      (fieldName) => fieldName !== this._descriptor.geoField
-    );
     const { docValueFields, sourceOnlyFields } = getDocValueAndSourceFields(
       indexPattern,
-      fieldNames,
+      requestMeta.fieldNames,
       'epoch_millis'
     );
 
@@ -537,6 +527,15 @@ export class ESSearchSource extends AbstractESSource implements IMvtVectorSource
     return indexSettings.maxResultWindow;
   }
 
+  /*
+   * Changes in requestMeta.fieldNames requires re-fetch.
+   * requestMeta.fieldNames are used to acheive smallest response possible.
+   * Response only includes fields required for client usage.
+   */
+  isFieldAware(): boolean {
+    return true;
+  }
+
   async getGeoJsonWithMeta(
     layerName: string,
     requestMeta: VectorSourceRequestMeta,
@@ -790,6 +789,7 @@ export class ESSearchSource extends AbstractESSource implements IMvtVectorSource
 
   getSyncMeta(): ESSearchSourceSyncMeta {
     return {
+      geoField: this._descriptor.geoField,
       filterByMapBounds: this._descriptor.filterByMapBounds,
       sortField: this._descriptor.sortField,
       sortOrder: this._descriptor.sortOrder,
@@ -879,19 +879,15 @@ export class ESSearchSource extends AbstractESSource implements IMvtVectorSource
     // use fields API
     searchSource.setField(
       'fields',
-      requestMeta.fieldNames
-        .filter((fieldName) => {
-          return fieldName !== this._descriptor.geoField;
-        })
-        .map((fieldName) => {
-          const field = dataView.fields.getByName(fieldName);
-          return field && field.type === 'date'
-            ? {
-                field: fieldName,
-                format: 'epoch_millis',
-              }
-            : fieldName;
-        })
+      requestMeta.fieldNames.map((fieldName) => {
+        const field = dataView.fields.getByName(fieldName);
+        return field && field.type === 'date'
+          ? {
+              field: fieldName,
+              format: 'epoch_millis',
+            }
+          : fieldName;
+      })
     );
 
     const mvtUrlServicePath = getHttp().basePath.prepend(`${MVT_GETTILE_API_PATH}/{z}/{x}/{y}.pbf`);

x-pack/plugins/maps/public/classes/sources/es_source/es_source.ts

@@ -129,10 +129,6 @@ export class AbstractESSource extends AbstractVectorSource implements IESSource
     return this._descriptor.applyForceRefresh;
   }
 
-  isFieldAware(): boolean {
-    return true;
-  }
-
   isQueryAware(): boolean {
     return true;
   }

x-pack/plugins/maps/public/classes/sources/join_sources/es_distance_source/es_distance_source.ts

@@ -15,13 +15,14 @@ import { getJoinAggKey } from '../../../../../common/get_agg_key';
 import { AbstractESAggSource } from '../../es_agg_source';
 import type { BucketProperties } from '../../../../../common/elasticsearch_util';
 import {
+  DataFilters,
   ESDistanceSourceDescriptor,
   VectorSourceRequestMeta,
 } from '../../../../../common/descriptor_types';
 import { PropertiesMap } from '../../../../../common/elasticsearch_util';
 import { isValidStringConfig } from '../../../util/valid_string_config';
 import { IJoinSource } from '../types';
-import type { IESAggSource } from '../../es_agg_source';
+import type { IESAggSource, ESAggsSourceSyncMeta } from '../../es_agg_source';
 import { IField } from '../../../fields/field';
 import { mergeExecutionContext } from '../../execution_context_utils';
 import { processDistanceResponse } from './process_distance_response';
@@ -29,7 +30,8 @@ import { isSpatialSourceComplete } from '../is_spatial_source_complete';
 
 export const DEFAULT_WITHIN_DISTANCE = 5;
 
-type ESDistanceSourceSyncMeta = Pick<ESDistanceSourceDescriptor, 'distance' | 'geoField'>;
+type ESDistanceSourceSyncMeta = ESAggsSourceSyncMeta &
+  Pick<ESDistanceSourceDescriptor, 'distance' | 'geoField'>;
 
 export class ESDistanceSource extends AbstractESAggSource implements IJoinSource, IESAggSource {
   static type = SOURCE_TYPES.ES_DISTANCE_SOURCE;
@@ -162,12 +164,9 @@ export class ESDistanceSource extends AbstractESAggSource implements IJoinSource
     return false;
   }
 
-  getFieldNames(): string[] {
-    return this.getMetricFields().map((esAggMetricField) => esAggMetricField.getName());
-  }
-
-  getSyncMeta(): ESDistanceSourceSyncMeta {
+  getSyncMeta(dataFilters: DataFilters): ESDistanceSourceSyncMeta {
     return {
+      ...super.getSyncMeta(dataFilters),
       distance: this._descriptor.distance,
       geoField: this._descriptor.geoField,
     };

x-pack/plugins/maps/public/classes/sources/join_sources/es_term_source/es_term_source.test.ts

@@ -6,6 +6,7 @@
  */
 
 import { AGG_TYPE } from '../../../../../common/constants';
+import { DataFilters } from '../../../../../common/descriptor_types';
 import type { BucketProperties, PropertiesMap } from '../../../../../common/elasticsearch_util';
 import { ESTermSource, extractPropertiesMap } from './es_term_source';
 
@@ -117,8 +118,9 @@ describe('getSyncMeta', () => {
       indexPatternId: 'foobar',
       size: 10,
     });
-    expect(source.getSyncMeta()).toEqual({
+    expect(source.getSyncMeta({} as unknown as DataFilters)).toEqual({
       indexPatternId: 'foobar',
+      metrics: ['__kbnjoin__count__1234'],
       size: 10,
       term: 'myTermField',
     });

x-pack/plugins/maps/public/classes/sources/join_sources/es_term_source/es_term_source.ts

@@ -25,13 +25,14 @@ import {
   BucketProperties,
 } from '../../../../../common/elasticsearch_util';
 import {
+  DataFilters,
   ESTermSourceDescriptor,
   VectorSourceRequestMeta,
 } from '../../../../../common/descriptor_types';
 import { PropertiesMap } from '../../../../../common/elasticsearch_util';
 import { isValidStringConfig } from '../../../util/valid_string_config';
 import { ITermJoinSource } from '../types';
-import type { IESAggSource } from '../../es_agg_source';
+import type { IESAggSource, ESAggsSourceSyncMeta } from '../../es_agg_source';
 import { IField } from '../../../fields/field';
 import { mergeExecutionContext } from '../../execution_context_utils';
 import { isTermSourceComplete } from './is_term_source_complete';
@@ -39,7 +40,8 @@ import { isTermSourceComplete } from './is_term_source_complete';
 const TERMS_AGG_NAME = 'join';
 const TERMS_BUCKET_KEYS_TO_IGNORE = ['key', 'doc_count'];
 
-type ESTermSourceSyncMeta = Pick<ESTermSourceDescriptor, 'indexPatternId' | 'size' | 'term'>;
+type ESTermSourceSyncMeta = ESAggsSourceSyncMeta &
+  Pick<ESTermSourceDescriptor, 'indexPatternId' | 'size' | 'term'>;
 
 export function extractPropertiesMap(rawEsData: any, countPropertyName: string): PropertiesMap {
   const propertiesMap: PropertiesMap = new Map<string, BucketProperties>();
@@ -184,12 +186,9 @@ export class ESTermSource extends AbstractESAggSource implements ITermJoinSource
     return `es_table ${this.getIndexPatternId()}`;
   }
 
-  getFieldNames(): string[] {
-    return this.getMetricFields().map((esAggMetricField) => esAggMetricField.getName());
-  }
-
-  getSyncMeta(): ESTermSourceSyncMeta {
+  getSyncMeta(dataFilters: DataFilters): ESTermSourceSyncMeta {
     return {
+      ...super.getSyncMeta(dataFilters),
       indexPatternId: this._descriptor.indexPatternId,
       size: this._descriptor.size,
       term: this._descriptor.term,

x-pack/plugins/maps/public/classes/sources/join_sources/table_source/table_source.ts

@@ -54,10 +54,6 @@ export class TableSource extends AbstractVectorSource implements ITermJoinSource
     return `table source ${uuidv4()}`;
   }
 
-  getSyncMeta(): null {
-    return null;
-  }
-
   async getPropertiesMap(
     requestMeta: VectorSourceRequestMeta,
     leftSourceName: string,
@@ -66,7 +62,9 @@ export class TableSource extends AbstractVectorSource implements ITermJoinSource
   ): Promise<PropertiesMap> {
     const propertiesMap: PropertiesMap = new Map<string, BucketProperties>();
 
-    const fieldNames = await this.getFieldNames();
+    const columnNames = this._descriptor.__columns.map((column) => {
+      return column.name;
+    });
 
     for (let i = 0; i < this._descriptor.__rows.length; i++) {
       const row: { [key: string]: string | number } = this._descriptor.__rows[i];
@@ -77,7 +75,7 @@ export class TableSource extends AbstractVectorSource implements ITermJoinSource
           if (key === this._descriptor.term && row[key]) {
             propKey = row[key];
           }
-          if (fieldNames.indexOf(key) >= 0 && key !== this._descriptor.term) {
+          if (columnNames.indexOf(key) >= 0 && key !== this._descriptor.term) {
             props[key] = row[key];
           }
         }
@@ -137,12 +135,6 @@ export class TableSource extends AbstractVectorSource implements ITermJoinSource
     });
   }
 
-  getFieldNames(): string[] {
-    return this._descriptor.__columns.map((column) => {
-      return column.name;
-    });
-  }
-
   hasTooltipProperties(): boolean {
     return false;
   }

x-pack/plugins/maps/public/classes/sources/join_sources/types.ts

@@ -10,7 +10,7 @@ import type { KibanaExecutionContext } from '@kbn/core/public';
 import { Query } from '@kbn/data-plugin/common/query';
 import { Adapters } from '@kbn/inspector-plugin/common/adapters';
 import { IField } from '../../fields/field';
-import { VectorSourceRequestMeta } from '../../../../common/descriptor_types';
+import { DataFilters, VectorSourceRequestMeta } from '../../../../common/descriptor_types';
 import { PropertiesMap } from '../../../../common/elasticsearch_util';
 import { ITooltipProperty } from '../../tooltips/tooltip_property';
 import { ISource } from '../source';
@@ -28,10 +28,9 @@ export interface IJoinSource extends ISource {
   ): Promise<PropertiesMap>;
 
   /*
-   * Vector layer avoids unnecessarily re-fetching join data.
-   * Use getSyncMeta to expose fields that require join data re-fetch when changed.
+   * Use getSyncMeta to expose join configurations that require join data re-fetch when changed.
    */
-  getSyncMeta(): object | null;
+  getSyncMeta(dataFilters: DataFilters): object | null;
 
   getId(): string;
   getRightFields(): IField[];

x-pack/plugins/maps/public/classes/sources/mvt_single_layer_vector_source/mvt_single_layer_vector_source.tsx

@@ -92,12 +92,6 @@ export class MVTSingleLayerVectorSource extends AbstractSource implements IMvtVe
     );
   }
 
-  getFieldNames(): string[] {
-    return this._descriptor.fields.map((field: MVTFieldDescriptor) => {
-      return field.name;
-    });
-  }
-
   addFeature(geometry: Geometry | Position[]): Promise<void> {
     throw new Error('Does not implement addFeature');
   }
@@ -191,8 +185,12 @@ export class MVTSingleLayerVectorSource extends AbstractSource implements IMvtVe
     return null;
   }
 
-  getSyncMeta(): null {
-    return null;
+  getSyncMeta() {
+    return {
+      mvtFields: this._descriptor.fields.map((field: MVTFieldDescriptor) => {
+        return field.name;
+      }),
+    };
   }
 
   isBoundsAware() {

x-pack/plugins/maps/public/classes/sources/source.ts

@@ -46,6 +46,13 @@ export type ImmutableSourceProperty = {
 export interface ISource {
   getDisplayName(): Promise<string>;
   getType(): string;
+  /*
+   * Re-fetch flag. When function returns true, source will re-fetch on requestMeta.fieldNames changes.
+   * Example uses of fieldNames change requiring re-fetch:
+   * 1) Data driven styling
+   * 2) Term join
+   * 3) Feature masking.
+   */
   isFieldAware(): boolean;
   isFilterByMapBounds(): boolean;
   isQueryAware(): boolean;
@@ -56,7 +63,6 @@ export interface ISource {
   renderSourceSettingsEditor(sourceEditorArgs: SourceEditorArgs): ReactElement<any> | null;
   supportsFitToBounds(): Promise<boolean>;
   cloneDescriptor(): AbstractSourceDescriptor;
-  getFieldNames(): string[];
   getApplyGlobalQuery(): boolean;
   getApplyGlobalTime(): boolean;
   getApplyForceRefresh(): boolean;
@@ -113,10 +119,6 @@ export class AbstractSource implements ISource {
     return false;
   }
 
-  getFieldNames(): string[] {
-    return [];
-  }
-
   renderSourceSettingsEditor(sourceEditorArgs: SourceEditorArgs): ReactElement<any> | null {
     return null;
   }

x-pack/plugins/maps/public/classes/sources/vector_source/vector_source.tsx

@@ -109,12 +109,10 @@ export interface IVectorSource extends ISource {
   supportsJoins(): boolean;
 
   /*
-   * Vector layer avoids unnecessarily re-fetching source data.
-   * Use getSyncMeta to expose fields that require source data re-fetch when changed.
+   * Use getSyncMeta to expose source configuration changes that require source data re-fetch when changed.
    */
   getSyncMeta(dataFilters: DataFilters): object | null;
 
-  getFieldNames(): string[];
   createField({ fieldName }: { fieldName: string }): IField;
   hasTooltipProperties(): boolean;
   getSupportedShapeTypes(): Promise<VECTOR_SHAPE_TYPE[]>;
@@ -141,10 +139,6 @@ export interface IVectorSource extends ISource {
 }
 
 export class AbstractVectorSource extends AbstractSource implements IVectorSource {
-  getFieldNames(): string[] {
-    return [];
-  }
-
   isMvt() {
     return false;
   }

x-pack/plugins/ml/public/maps/anomaly_source.tsx

@@ -185,12 +185,10 @@ export class AnomalySource implements IVectorSource {
     return false;
   }
 
-  getFieldNames(): string[] {
-    return Object.keys(ANOMALY_SOURCE_FIELDS);
-  }
-
   async getFields(): Promise<IField[]> {
-    return this.getFieldNames().map((field) => new AnomalySourceField({ source: this, field }));
+    return Object.keys(ANOMALY_SOURCE_FIELDS).map(
+      (field) => new AnomalySourceField({ source: this, field })
+    );
   }
 
   getGeoGridPrecision(zoom: number): number {