MCP Data Catalog

import type { FieldName } from '../value-objects/field-name.js'; import type { QueryResultRow } from '../entities/query-result.js'; /** * Service for projecting (selecting) specific fields from dataset rows. * * Handles field selection to limit the data returned to only the * fields requested by the client. */ export class ProjectionService { /** * Project rows to include only specified fields. * * @param rows - The rows to project * @param fields - The fields to include in the result * @returns Rows with only the specified fields */ projectRows(rows: QueryResultRow[], fields: FieldName[]): QueryResultRow[] { if (fields.length === 0) { return rows; } return rows.map((row) => this.projectRow(row, fields)); } /** * Project a single row to include only specified fields. * * @param row - The row to project * @param fields - The fields to include * @returns A new row with only the specified fields */ private projectRow(row: QueryResultRow, fields: FieldName[]): QueryResultRow { const projectedRow: QueryResultRow = {}; for (const field of fields) { projectedRow[field] = row[field]; } return projectedRow; } }