add a toggle to filter empty schemas and db

frontend/src/components/datasources/__tests__/filter-empty.test.ts

@@ -0,0 +1,183 @@
+/* Copyright 2026 Marimo. All rights reserved. */
+
+import { describe, expect, it } from "vitest";
+import type {
+  Database,
+  DatabaseSchema,
+  DataTable,
+} from "@/core/kernel/messages";
+import { filterEmptyDatabases } from "../datasources";
+
+function makeTable(name: string): DataTable {
+  return {
+    name,
+    columns: [],
+    source: "memory",
+    source_type: "local",
+    type: "table",
+    engine: null,
+    indexes: null,
+    num_columns: null,
+    num_rows: null,
+    variable_name: null,
+    primary_keys: null,
+  };
+}
+
+function makeSchema(opts: {
+  name: string;
+  tables: DataTable[];
+  tables_resolved?: boolean;
+}): DatabaseSchema {
+  return {
+    name: opts.name,
+    tables: opts.tables,
+    tables_resolved: opts.tables_resolved ?? true,
+  };
+}
+
+function makeDatabase(
+  name: string,
+  schemas: DatabaseSchema[],
+  schemas_resolved = true,
+): Database {
+  return {
+    name,
+    dialect: "duckdb",
+    schemas,
+    schemas_resolved,
+    engine: null,
+  };
+}
+
+describe("filterEmptyDatabases", () => {
+  it("hides schemas whose tables are resolved and empty", () => {
+    const databases = [
+      makeDatabase("memory", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+        makeSchema({ name: "empty_schema", tables: [] }),
+      ]),
+    ];
+
+    expect(filterEmptyDatabases(databases)).toEqual([
+      makeDatabase("memory", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+      ]),
+    ]);
+  });
+
+  it("preserves databases whose schemas have not been resolved yet (lazy state)", () => {
+    const databases = [
+      makeDatabase("not_loaded_yet", [], /* schemas_resolved */ false),
+    ];
+
+    expect(filterEmptyDatabases(databases)).toEqual([
+      makeDatabase("not_loaded_yet", [], false),
+    ]);
+  });
+
+  it("hides databases that have been resolved as empty", () => {
+    const databases = [
+      makeDatabase("really_empty", [], /* schemas_resolved */ true),
+      makeDatabase("has_tables", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+      ]),
+    ];
+
+    expect(filterEmptyDatabases(databases)).toEqual([
+      makeDatabase("has_tables", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+      ]),
+    ]);
+  });
+
+  it("hides databases whose schemas all filtered to empty", () => {
+    const databases = [
+      makeDatabase("only_empty", [
+        makeSchema({ name: "a", tables: [] }),
+        makeSchema({ name: "b", tables: [] }),
+      ]),
+      makeDatabase("has_tables", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+      ]),
+    ];
+
+    expect(filterEmptyDatabases(databases)).toEqual([
+      makeDatabase("has_tables", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+      ]),
+    ]);
+  });
+
+  it("treats missing schemas_resolved as resolved (backward compatible)", () => {
+    const databases = [
+      { name: "memory", dialect: "duckdb", schemas: [], engine: null },
+    ] as Database[];
+
+    expect(filterEmptyDatabases(databases)).toEqual([]);
+  });
+
+  it("preserves schemas whose tables have not been resolved yet", () => {
+    const databases = [
+      makeDatabase("snowflake_db", [
+        // include_tables=False was used; the schema is not actually empty,
+        // tables will be fetched lazily on expand.
+        makeSchema({ name: "public", tables: [], tables_resolved: false }),
+        makeSchema({ name: "audit", tables: [], tables_resolved: false }),
+        makeSchema({
+          name: "really_empty",
+          tables: [],
+          tables_resolved: true,
+        }),
+      ]),
+    ];
+
+    expect(filterEmptyDatabases(databases)).toEqual([
+      makeDatabase("snowflake_db", [
+        makeSchema({ name: "public", tables: [], tables_resolved: false }),
+        makeSchema({ name: "audit", tables: [], tables_resolved: false }),
+      ]),
+    ]);
+  });
+
+  it("treats missing tables_resolved as resolved (backward compatible)", () => {
+    // Older payloads predating the new flag may omit it; default semantics
+    // treat the schema as resolved/authoritative.
+    const databases = [
+      makeDatabase("memory", [
+        { name: "main", tables: [makeTable("t1")] },
+        { name: "empty_schema", tables: [] },
+      ] as DatabaseSchema[]),
+    ];
+
+    expect(filterEmptyDatabases(databases)).toEqual([
+      makeDatabase("memory", [
+        { name: "main", tables: [makeTable("t1")] },
+      ] as DatabaseSchema[]),
+    ]);
+  });
+
+  it("returns the same reference when nothing was filtered", () => {
+    const databases = [
+      makeDatabase("memory", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+      ]),
+    ];
+
+    expect(filterEmptyDatabases(databases)).toBe(databases);
+  });
+
+  it("does not mutate the input", () => {
+    const databases = [
+      makeDatabase("memory", [
+        makeSchema({ name: "main", tables: [makeTable("t1")] }),
+        makeSchema({ name: "empty_schema", tables: [] }),
+      ]),
+    ];
+    const snapshot = JSON.parse(JSON.stringify(databases));
+
+    filterEmptyDatabases(databases);
+
+    expect(databases).toEqual(snapshot);
+  });
+});

frontend/src/components/datasources/datasources.tsx

@@ -1,8 +1,15 @@
 /* Copyright 2026 Marimo. All rights reserved. */
 
 import { CommandList } from "cmdk";
-import { atom, useAtomValue, useSetAtom } from "jotai";
-import { PlusIcon, PlusSquareIcon, XIcon } from "lucide-react";
+import { atom, useAtom, useAtomValue, useSetAtom } from "jotai";
+import { atomWithStorage } from "jotai/utils";
+import {
+  EyeIcon,
+  EyeOffIcon,
+  PlusIcon,
+  PlusSquareIcon,
+  XIcon,
+} from "lucide-react";
 import React from "react";
 import { dbDisplayName } from "@/components/databases/display";
 import { EngineVariable } from "@/components/databases/engine-variable";
@@ -52,6 +59,7 @@ import { sortBy } from "@/utils/arrays";
 import { logNever } from "@/utils/assertNever";
 import { cn } from "@/utils/cn";
 import { Events } from "@/utils/events";
+import { jotaiJsonStorage } from "@/utils/storage/jotai";
 import {
   DatabaseIcon,
   SchemaIcon,
@@ -116,6 +124,63 @@ const sortedTablesAtom = atom((get) => {
   });
 });
 
+/**
+ * Whether to hide empty schemas and databases (those with no tables) in the
+ * datasources panel.
+ */
+export const hideEmptyDatasourcesAtom = atomWithStorage<boolean>(
+  "marimo:datasources:hideEmpty",
+  false,
+  jotaiJsonStorage,
+  { getOnInit: true },
+);
+
+function isKnownEmptySchema(schema: DatabaseSchema): boolean {
+  return schema.tables_resolved !== false && schema.tables.length === 0;
+}
+
+/**
+ * Apply the "hide empty" filter to a connection's databases.
+ *
+ * - Schemas with confirmed-empty table lists are hidden.
+ * - Databases are hidden when either (a) their schemas have been enumerated
+ *   and the list is empty, or (b) every schema in them was hidden by the
+ *   schema-level filter.
+ * - Databases / schemas whose contents haven't been resolved yet (deferred
+ *   discovery — `schemas_resolved === false` or `tables_resolved === false`)
+ *   are preserved so the user can expand them to trigger a fetch.
+ */
+export function filterEmptyDatabases(databases: Database[]): Database[] {
+  let changed = false;
+  const result: Database[] = [];
+  for (const database of databases) {
+    // Known-empty database: schema list was enumerated and is empty.
+    if (database.schemas_resolved !== false && database.schemas.length === 0) {
+      changed = true;
+      continue;
+    }
+    // Deferred schema discovery — keep so the user can expand and load.
+    if (database.schemas.length === 0) {
+      result.push(database);
+      continue;
+    }
+    const visibleSchemas = database.schemas.filter(
+      (schema) => !isKnownEmptySchema(schema),
+    );
+    if (visibleSchemas.length === 0) {
+      changed = true;
+      continue;
+    }
+    if (visibleSchemas.length === database.schemas.length) {
+      result.push(database);
+      continue;
+    }
+    changed = true;
+    result.push({ ...database, schemas: visibleSchemas });
+  }
+  return changed ? result : databases;
+}
+
 /**
  * This atom is used to get the data connections that are available to the user.
  * It filters out the internal engines if it has no databases or if it has only the in-memory database and no schemas.
@@ -152,10 +217,27 @@ export const connectionsAtom = atom((get) => {
 
 export const DataSources: React.FC = () => {
   const [searchValue, setSearchValue] = React.useState<string>("");
+  const [hideEmpty, setHideEmpty] = useAtom(hideEmptyDatasourcesAtom);
 
   const closeAllColumns = useSetAtom(closeAllColumnsAtom);
   const tables = useAtomValue(sortedTablesAtom);
-  const dataConnections = useAtomValue(connectionsAtom);
+  const rawConnections = useAtomValue(connectionsAtom);
+
+  const dataConnections = React.useMemo(() => {
+    if (!hideEmpty) {
+      return rawConnections;
+    }
+    let changed = false;
+    const filtered = rawConnections.map((connection) => {
+      const databases = filterEmptyDatabases(connection.databases);
+      if (databases === connection.databases) {
+        return connection;
+      }
+      changed = true;
+      return { ...connection, databases };
+    });
+    return changed ? filtered : rawConnections;
+  }, [rawConnections, hideEmpty]);
 
   if (tables.length === 0 && dataConnections.length === 0) {
     return (
@@ -204,6 +286,28 @@ export const DataSources: React.FC = () => {
           </button>
         )}
 
+        <Tooltip
+          content={
+            hideEmpty
+              ? "Show empty schemas and databases"
+              : "Hide empty schemas and databases"
+          }
+        >
+          <Button
+            data-testid="datasources-hide-empty-button"
+            variant="ghost"
+            size="sm"
+            className="px-2 rounded-none focus-visible:outline-hidden"
+            onClick={() => setHideEmpty(!hideEmpty)}
+          >
+            {hideEmpty ? (
+              <EyeOffIcon className="h-4 w-4" />
+            ) : (
+              <EyeIcon className="h-4 w-4" />
+            )}
+          </Button>
+        </Tooltip>
+
         <AddConnectionDialog>
           <Button
             variant="ghost"

frontend/src/core/datasets/data-source-connections.ts

@@ -169,6 +169,7 @@ const {
         return {
           ...db,
           schemas: schemas,
+          schemas_resolved: true,
         };
       }),
     };
@@ -213,6 +214,7 @@ const {
             return {
               ...schema,
               tables: tables,
+              tables_resolved: true,
             };
           }),
         };

marimo/_data/models.py

@@ -85,8 +85,19 @@ class DataTable(BaseStruct):
 
 
 class Schema(BaseStruct):
+    """
+    Represents a database schema and its tables.
+
+    Attributes:
+        name (str): The name of the schema.
+        tables (List[DataTable]): Tables in this schema.
+        tables_resolved (bool): True when `tables` has been enumerated
+            False when table discovery was deferred. Defaults to True
+    """
+
     name: str
     tables: list[DataTable]
+    tables_resolved: bool = True
 
 
 class Database(BaseStruct):
@@ -96,13 +107,16 @@ class Database(BaseStruct):
     Attributes:
         name (str): The name of the database
         dialect (str): The dialect of the database
-        schemas (List[Schema]): List of schemas in the database
+        schemas (List[Schema]): List of schemas in the database.
+        schemas_resolved (bool): True when `schemas` has been enumerated.
+            False when schema discovery was deferred. Defaults to True
         engine (Optional[VariableName]): Database engine or connection handler, if any.
     """
 
     name: str
     dialect: str
     schemas: list[Schema]
+    schemas_resolved: bool = True
     engine: VariableName | None = None
 
 

marimo/_sql/connection_utils.py

@@ -56,6 +56,7 @@ def update_schema_list_in_connection(
                 continue
 
             database.schemas = updated_schema_list
+            database.schemas_resolved = True
             return
 
 
@@ -84,4 +85,5 @@ def update_table_list_in_connection(
                     continue
 
                 schema.tables = updated_table_list
+                schema.tables_resolved = True
                 return