feat: add datasource schema read methods

packages/cubejs-query-orchestrator/src/orchestrator/QueryCache.ts

@@ -18,7 +18,7 @@ import { LocalCacheDriver } from './LocalCacheDriver';
 import { DriverFactory, DriverFactoryByDataSource } from './DriverFactory';
 import { LoadPreAggregationResult, PreAggregationDescription } from './PreAggregations';
 import { getCacheHash } from './utils';
-import { CacheAndQueryDriverType } from './QueryOrchestrator';
+import { CacheAndQueryDriverType, MetadataOperationType } from './QueryOrchestrator';
 
 type QueryOptions = {
   external?: boolean;
@@ -567,8 +567,36 @@ export class QueryCache {
   ): QueryQueue {
     const queue: any = new QueryQueue(redisPrefix, {
       queryHandlers: {
+        metadata: async (req, _setCancelHandle) => {
+          const client = await clientFactory();
+          const { operation } = req;
+          const params = req.params || {};
+
+          switch (operation) {
+            case MetadataOperationType.GET_SCHEMAS:
+              queue.logger('Getting datasource schemas', { dataSource: req.dataSource, requestId: req.requestId });
+              return client.getSchemas();
+            case MetadataOperationType.GET_TABLES_FOR_SCHEMAS:
+              queue.logger('Getting tables for schemas', {
+                dataSource: req.dataSource,
+                schemaCount: params.schemas?.length || 0,
+                requestId: req.requestId
+              });
+              return client.getTablesForSpecificSchemas(params.schemas);
+            case MetadataOperationType.GET_COLUMNS_FOR_TABLES:
+              queue.logger('Getting columns for tables', {
+                dataSource: req.dataSource,
+                tableCount: params.tables?.length || 0,
+                requestId: req.requestId
+              });
+              return client.getColumnsForSpecificTables(params.tables);
+            default:
+              throw new Error(`Unknown metadata operation: ${operation}`);
+          }
+        },
         query: async (req, setCancelHandle) => {
           const client = await clientFactory();
+
           const resultPromise = executeFn(client, req);
           let handle;
           if (resultPromise.cancel) {
@@ -636,6 +664,12 @@ export class QueryCache {
         }));
       },
       cancelHandlers: {
+        metadata: async (req) => {
+          if (req.cancelHandler && queue.handles[req.cancelHandler]) {
+            await queue.handles[req.cancelHandler].cancel();
+            delete queue.handles[req.cancelHandler];
+          }
+        },
         query: async (req) => {
           if (req.cancelHandler && queue.handles[req.cancelHandler]) {
             await queue.handles[req.cancelHandler].cancel();

packages/cubejs-query-orchestrator/src/orchestrator/QueryOrchestrator.ts

@@ -2,9 +2,13 @@ import * as stream from 'stream';
 import R from 'ramda';
 import { getEnv } from '@cubejs-backend/shared';
 import { CubeStoreDriver } from '@cubejs-backend/cubestore-driver';
+import {
+  QuerySchemasResult,
+  QueryTablesResult,
+  QueryColumnsResult,
+  QueryKey } from '@cubejs-backend/base-driver';
 
-import { QueryKey } from '@cubejs-backend/base-driver';
-import { QueryCache, QueryBody, TempTable, PreAggTableToTempTable } from './QueryCache';
+import { QueryCache, QueryBody, TempTable, PreAggTableToTempTable, QueryWithParams, CacheKey } from './QueryCache';
 import { PreAggregations, PreAggregationDescription, getLastUpdatedAtTimestamp } from './PreAggregations';
 import { DriverFactory, DriverFactoryByDataSource } from './DriverFactory';
 import { QueryStream } from './QueryStream';
@@ -17,6 +21,12 @@ export enum DriverType {
   Cache = 'cache',
 }
 
+export enum MetadataOperationType {
+  GET_SCHEMAS = 'GET_SCHEMAS',
+  GET_TABLES_FOR_SCHEMAS = 'GET_TABLES_FOR_SCHEMAS',
+  GET_COLUMNS_FOR_TABLES = 'GET_COLUMNS_FOR_TABLES'
+}
+
 export interface QueryOrchestratorOptions {
   externalDriverFactory?: DriverFactory;
   cacheAndQueueDriver?: CacheAndQueryDriverType;
@@ -428,4 +438,120 @@ export class QueryOrchestrator {
   public async updateRefreshEndReached() {
     return this.preAggregations.updateRefreshEndReached();
   }
+
+  private createMetadataQuery(operation: string, params: Record<string, any>): QueryWithParams {
+    return [
+      `METADATA:${operation}`,
+      // TODO: Metadata queries need object params like [{ schema, table }]
+      // but QueryWithParams expects string[]. This forces JSON.stringify workaround.
+      [JSON.stringify(params)],
+      { external: false, renewalThreshold: 24 * 60 * 60 }
+    ];
+  }
+
+  private async queryDataSourceMetadata<T>(
+    operation: MetadataOperationType,
+    params: Record<string, any>,
+    dataSource: string = 'default',
+    options: {
+      requestId?: string;
+      forceRefresh?: boolean;
+      renewalThreshold?: number;
+      expiration?: number;
+    } = {}
+  ): Promise<T> {
+    const {
+      requestId,
+      forceRefresh = false,
+      renewalThreshold = 24 * 60 * 60,
+      expiration = 7 * 24 * 60 * 60,
+    } = options;
+
+    const metadataQuery = this.createMetadataQuery(operation, params);
+    const cacheKey: CacheKey = [metadataQuery, dataSource];
+
+    const renewalKey = forceRefresh ? undefined : [
+      `METADATA_RENEWAL:${operation}`,
+      dataSource,
+      Math.floor(Date.now() / (renewalThreshold * 1000))
+    ];
+
+    return this.queryCache.cacheQueryResult(
+      metadataQuery,
+      [],
+      cacheKey,
+      expiration,
+      {
+        renewalThreshold,
+        renewalKey,
+        forceNoCache: forceRefresh,
+        requestId,
+        dataSource,
+        useInMemory: true,
+        waitForRenew: true,
+      }
+    );
+  }
+
+  /**
+   * Query the data source for available schemas.
+   */
+  public async queryDataSourceSchemas(
+    dataSource: string = 'default',
+    options: {
+      requestId?: string;
+      forceRefresh?: boolean;
+      renewalThreshold?: number;
+      expiration?: number;
+    } = {}
+  ): Promise<QuerySchemasResult[]> {
+    return this.queryDataSourceMetadata<QuerySchemasResult[]>(
+      MetadataOperationType.GET_SCHEMAS,
+      {},
+      dataSource,
+      options
+    );
+  }
+
+  /**
+   * Query the data source for tables within the specified schemas.
+   */
+  public async queryTablesForSchemas(
+    schemas: QuerySchemasResult[],
+    dataSource: string = 'default',
+    options: {
+      requestId?: string;
+      forceRefresh?: boolean;
+      renewalThreshold?: number;
+      expiration?: number;
+    } = {}
+  ): Promise<QueryTablesResult[]> {
+    return this.queryDataSourceMetadata<QueryTablesResult[]>(
+      MetadataOperationType.GET_TABLES_FOR_SCHEMAS,
+      { schemas },
+      dataSource,
+      options
+    );
+  }
+
+  /**
+   * Query the data source for columns within the specified tables.
+   */
+  public async queryColumnsForTables(
+    tables: QueryTablesResult[],
+    dataSource: string = 'default',
+    options: {
+      requestId?: string;
+      forceRefresh?: boolean;
+      renewalThreshold?: number;
+      expiration?: number;
+    } = {}
+  ): Promise<QueryColumnsResult[]> {
+    return this.queryDataSourceMetadata<QueryColumnsResult[]>(
+      MetadataOperationType.GET_COLUMNS_FOR_TABLES,
+      { tables },
+      dataSource,
+      options
+    );
+  }
 }