feat(java): add table names java api (#1279)

Add lancedb-jni and table names API

---------

Co-authored-by: Lei Xu <eddyxu@gmail.com>

java/core/src/main/java/com/lancedb/lancedb/Connection.java

@@ -0,0 +1,120 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.lancedb.lancedb;
+
+import io.questdb.jar.jni.JarJniLoader;
+import java.io.Closeable;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Represents LanceDB database.
+ */
+public class Connection implements Closeable {
+  static {
+    JarJniLoader.loadLib(Connection.class, "/nativelib", "lancedb_jni");
+  }
+
+  private long nativeConnectionHandle;
+
+  /**
+   * Connect to a LanceDB instance.
+   */
+  public static native Connection connect(String uri);
+
+  /**
+   * Get the names of all tables in the database. The names are sorted in
+   * ascending order.
+   *
+   * @return the table names
+   */
+  public List<String> tableNames() {
+    return tableNames(Optional.empty(), Optional.empty());
+  }
+
+  /**
+   * Get the names of filtered tables in the database. The names are sorted in
+   * ascending order.
+   *
+   * @param limit The number of results to return.
+   * @return the table names
+   */
+  public List<String> tableNames(int limit) {
+    return tableNames(Optional.empty(), Optional.of(limit));
+  }
+
+  /**
+   * Get the names of filtered tables in the database. The names are sorted in
+   * ascending order.
+   *
+   * @param startAfter If present, only return names that come lexicographically after the supplied
+   *                   value. This can be combined with limit to implement pagination
+   *                   by setting this to the last table name from the previous page.
+   * @return the table names
+   */
+  public List<String> tableNames(String startAfter) {
+    return tableNames(Optional.of(startAfter), Optional.empty());
+  }
+
+  /**
+   * Get the names of filtered tables in the database. The names are sorted in
+   * ascending order.
+   *
+   * @param startAfter If present, only return names that come lexicographically after the supplied
+   *                   value. This can be combined with limit to implement pagination
+   *                   by setting this to the last table name from the previous page.
+   * @param limit The number of results to return.
+   * @return the table names
+   */
+  public List<String> tableNames(String startAfter, int limit) {
+    return tableNames(Optional.of(startAfter), Optional.of(limit));
+  }
+
+  /**
+   * Get the names of filtered tables in the database. The names are sorted in
+   * ascending order.
+   *
+   * @param startAfter If present, only return names that come lexicographically after the supplied
+   *                   value. This can be combined with limit to implement pagination
+   *                   by setting this to the last table name from the previous page.
+   * @param limit The number of results to return.
+   * @return the table names
+   */
+  public native List<String> tableNames(
+      Optional<String> startAfter, Optional<Integer> limit);
+
+  /**
+   * Closes this connection and releases any system resources associated with it. If
+   * the connection is
+   * already closed, then invoking this method has no effect.
+   */
+  @Override
+  public void close() {
+    if (nativeConnectionHandle != 0) {
+      releaseNativeConnection(nativeConnectionHandle);
+      nativeConnectionHandle = 0;
+    }
+  }
+
+  /**
+   * Native method to release the Lance connection resources associated with the
+   * given handle.
+   *
+   * @param handle The native handle to the connection resource.
+   */
+  private native void releaseNativeConnection(long handle);
+
+  private Connection() {}
+}

java/core/src/test/java/com/lancedb/lancedb/ConnectionTest.java

@@ -0,0 +1,135 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.lancedb.lancedb;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.nio.file.Path;
+import java.util.List;
+import java.net.URL;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+public class ConnectionTest {
+  private static final String[] TABLE_NAMES = {
+      "dataset_version",
+      "new_empty_dataset",
+      "test",
+      "write_stream"
+  };
+
+  @TempDir
+  static Path tempDir; // Temporary directory for the tests
+  private static URL lanceDbURL;
+
+  @BeforeAll
+  static void setUp() {
+    ClassLoader classLoader = ConnectionTest.class.getClassLoader();
+    lanceDbURL = classLoader.getResource("example_db");
+  }
+
+  @Test
+  void emptyDB() {
+    String databaseUri = tempDir.resolve("emptyDB").toString();
+    try (Connection conn = Connection.connect(databaseUri)) {
+      List<String> tableNames = conn.tableNames();
+      assertTrue(tableNames.isEmpty());
+    }
+  }
+
+  @Test
+  void tableNames() {
+    try (Connection conn = Connection.connect(lanceDbURL.toString())) {
+      List<String> tableNames = conn.tableNames();
+      assertEquals(4, tableNames.size());
+      for (int i = 0; i < TABLE_NAMES.length; i++) {
+        assertEquals(TABLE_NAMES[i], tableNames.get(i));
+      }
+    }
+  }
+
+  @Test
+  void tableNamesStartAfter() {
+    try (Connection conn = Connection.connect(lanceDbURL.toString())) {
+      assertTableNamesStartAfter(conn, TABLE_NAMES[0], 3, TABLE_NAMES[1], TABLE_NAMES[2], TABLE_NAMES[3]);
+      assertTableNamesStartAfter(conn, TABLE_NAMES[1], 2, TABLE_NAMES[2], TABLE_NAMES[3]);
+      assertTableNamesStartAfter(conn, TABLE_NAMES[2], 1, TABLE_NAMES[3]);
+      assertTableNamesStartAfter(conn, TABLE_NAMES[3], 0);
+      assertTableNamesStartAfter(conn, "a_dataset", 4, TABLE_NAMES[0], TABLE_NAMES[1], TABLE_NAMES[2], TABLE_NAMES[3]);
+      assertTableNamesStartAfter(conn, "o_dataset", 2, TABLE_NAMES[2], TABLE_NAMES[3]);
+      assertTableNamesStartAfter(conn, "v_dataset", 1, TABLE_NAMES[3]);
+      assertTableNamesStartAfter(conn, "z_dataset", 0);
+    }
+  }
+
+  private void assertTableNamesStartAfter(Connection conn, String startAfter, int expectedSize, String... expectedNames) {
+    List<String> tableNames = conn.tableNames(startAfter);
+    assertEquals(expectedSize, tableNames.size());
+    for (int i = 0; i < expectedNames.length; i++) {
+      assertEquals(expectedNames[i], tableNames.get(i));
+    }
+  }
+
+  @Test
+  void tableNamesLimit() {
+      try (Connection conn = Connection.connect(lanceDbURL.toString())) {
+      for (int i = 0; i <= TABLE_NAMES.length; i++) {
+        List<String> tableNames = conn.tableNames(i);
+        assertEquals(i, tableNames.size());
+        for (int j = 0; j < i; j++) {
+          assertEquals(TABLE_NAMES[j], tableNames.get(j));
+        }
+      }
+    }
+  }
+
+  @Test
+  void tableNamesStartAfterLimit() {
+    try (Connection conn = Connection.connect(lanceDbURL.toString())) {
+      List<String> tableNames = conn.tableNames(TABLE_NAMES[0], 2);
+      assertEquals(2, tableNames.size());
+      assertEquals(TABLE_NAMES[1], tableNames.get(0));
+      assertEquals(TABLE_NAMES[2], tableNames.get(1));
+      tableNames = conn.tableNames(TABLE_NAMES[1], 1);
+      assertEquals(1, tableNames.size());
+      assertEquals(TABLE_NAMES[2], tableNames.get(0));
+      tableNames = conn.tableNames(TABLE_NAMES[2], 2);
+      assertEquals(1, tableNames.size());
+      assertEquals(TABLE_NAMES[3], tableNames.get(0));
+      tableNames = conn.tableNames(TABLE_NAMES[3], 2);
+      assertEquals(0, tableNames.size());
+      tableNames = conn.tableNames(TABLE_NAMES[0], 0);
+      assertEquals(0, tableNames.size());
+
+      // Limit larger than the number of remaining tables
+      tableNames = conn.tableNames(TABLE_NAMES[0], 10);
+      assertEquals(3, tableNames.size());
+      assertEquals(TABLE_NAMES[1], tableNames.get(0));
+      assertEquals(TABLE_NAMES[2], tableNames.get(1));
+      assertEquals(TABLE_NAMES[3], tableNames.get(2));
+
+      // Start after a value not in the list
+      tableNames = conn.tableNames("non_existent_table", 2);
+      assertEquals(2, tableNames.size());
+      assertEquals(TABLE_NAMES[2], tableNames.get(0));
+      assertEquals(TABLE_NAMES[3], tableNames.get(1));
+
+      // Start after the last table with a limit
+      tableNames = conn.tableNames(TABLE_NAMES[3], 1);
+      assertEquals(0, tableNames.size());
+    }
+  }
+}

java/core/src/test/resources/example_db/dataset_version.lance/_transactions/0-d51afd07-e3cd-4c76-9b9b-787e13fd55b0.txn

@@ -0,0 +1 @@
+$d51afd07-e3cd-4c76-9b9b-787e13fd55b0<62>=id <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
*int320
8
name
 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
*string0
8

java/core/src/test/resources/example_db/new_empty_dataset.lance/_transactions/0-15648e72-076f-4ef1-8b90-10d305b95b3b.txn

@@ -0,0 +1 @@
+$15648e72-076f-4ef1-8b90-10d305b95b3b<33>=id <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
*int320
8
name
 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
*string0
8

java/core/src/test/resources/example_db/test.lance/_transactions/0-a3689caf-4f6b-4afc-a3c7-97af75661843.txn

@@ -0,0 +1 @@
+$a3689caf-4f6b-4afc-a3c7-97af75661843<34>oitem <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
*string8price
 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
*double8
0vector <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
*fixed_size_list:float:28