Data Explorer: Do not send backend empty schema, data, profile requests

extensions/positron-duckdb/src/extension.ts

@@ -276,7 +276,7 @@ END`;
 			numRows = upperLimit - lowerLimit + 1;
 		}
 
-		// No column selectors case -- TODO: why is the backend even sending this?
+		// No column selectors case, do not error if we get a request like this
 		if (columnSelectors.length === 0) {
 			return { columns: [] };
 		} else if (numRows === 0) {

src/vs/workbench/services/languageRuntime/common/languageRuntimeDataExplorerClient.ts

@@ -317,6 +317,10 @@ export class DataExplorerClientInstance extends Disposable {
 	 * @returns A promise that resolves to the table schema.
 	 */
 	async getSchema(columnIndices: Array<number>): Promise<TableSchema> {
+		if (columnIndices.length === 0) {
+			// Do not send backend requests for an empty selection
+			return { columns: [] };
+		}
 		return this.runBackendTask(
 			() => this._backendClient.getSchema(columnIndices),
 			() => ({ columns: [] })
@@ -365,6 +369,10 @@ export class DataExplorerClientInstance extends Disposable {
 	 * @returns A Promise<TableData> that resolves when the operation is complete.
 	 */
 	async getDataValues(columns: Array<ColumnSelection>): Promise<TableData> {
+		if (columns.length === 0) {
+			// Do not send backend requests for an empty selection
+			return { columns: [] };
+		}
 		return this.runBackendTask(
 			() => this._backendClient.getDataValues(columns, this._dataFormatOptions),
 			() => ({ columns: [[]] })
@@ -395,6 +403,10 @@ export class DataExplorerClientInstance extends Disposable {
 	async getColumnProfiles(
 		profiles: Array<ColumnProfileRequest>
 	): Promise<Array<ColumnProfileResult>> {
+		if (profiles.length === 0) {
+			// Do not send backend a request if empty array passed
+			return [];
+		}
 		return this.runBackendTask(
 			async () => {
 				const callbackId = generateUuid();

src/vs/workbench/services/positronDataExplorer/common/tableDataCache.ts

@@ -401,14 +401,14 @@ export class TableDataCache extends Disposable {
 			}
 		}
 
-		// Load the column schemas we need to load.
-		const tableSchema = await this._dataExplorerClientInstance.getSchema(columnIndices);
-
 		// Clear the column schema cache, if we're supposed to.
 		if (invalidateColumnSchemaCache) {
 			this._columnSchemaCache.clear();
 		}
 
+		// Load the column schemas we need to load.
+		const tableSchema = await this._dataExplorerClientInstance.getSchema(columnIndices);
+
 		// Cache the column schemas that were returned.
 		for (let i = 0; i < tableSchema.columns.length; i++) {
 			// Get the column schema and compute the column index.
@@ -501,9 +501,6 @@ export class TableDataCache extends Disposable {
 			}
 		}
 
-		// Get the data values.
-		const tableData = await this._dataExplorerClientInstance.getDataValues(columnSelections);
-
 		// Get the row labels.
 		let rowLabels: ArraySelection | undefined;
 		if (!tableState.has_row_labels) {
@@ -556,6 +553,9 @@ export class TableDataCache extends Disposable {
 			this._dataColumnCache.clear();
 		}
 
+		// Get the data values
+		const tableData = await this._dataExplorerClientInstance.getDataValues(columnSelections);
+
 		// Update the data column cache.
 		for (let column = 0; column < tableData.columns.length; column++) {
 			// Get the column selection.