[typo][samples](docs)(java) add read bitmap sample and update document. (#19005)

samples/read_bitmap/java/ReadBitmap.java

@@ -0,0 +1,145 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+import org.roaringbitmap.RoaringBitmap;
+import org.roaringbitmap.longlong.Roaring64NavigableMap;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.ResultSet;
+import java.sql.Statement;
+
+/**
+ * Prepare the table and data in Doris:
+ *
+ * <pre>
+ * {@code
+ * CREATE TABLE `t_bitmap` (
+ *   `rn` int(11) NULL,
+ *   `uids` bitmap BITMAP_UNION NULL
+ * ) AGGREGATE KEY(`rn`)
+ * DISTRIBUTED BY HASH(`rn`) BUCKETS 1
+ * PROPERTIES (
+ *   "replication_num" = "1"
+ * );
+ *
+ * INSERT INTO t_bitmap VALUES
+ * (0, bitmap_empty()),
+ * (1, to_bitmap(243)),
+ * (2, bitmap_from_array([1,2,3,4,5,434543])),
+ * (3, to_bitmap(287667876573)),
+ * (4, bitmap_from_array([487667876573, 387627876573, 987567876573, 187667876573]));
+ * }
+ * </pre>
+ *
+ * The pom.xml dependency:
+ * <pre>
+ * {@code
+ * <dependency>
+ *    <groupId>mysql</groupId>
+ *    <artifactId>mysql-connector-java</artifactId>
+ *    <version>8.0.28</version>
+ * </dependency>
+ * <dependency>
+ *    <groupId>org.roaringbitmap</groupId>
+ *    <artifactId>RoaringBitmap</artifactId>
+ *    <version>0.9.39</version>
+ * </dependency>
+ * }
+ * </pre>
+ */
+public class ReadBitmap {
+    public static void main(String[] args) throws Exception {
+
+        try (Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:9030/test?user=root");
+             Statement stmt = conn.createStatement()
+        ) {
+            stmt.execute("set return_object_data_as_binary=true"); // IMPORTANT!!!
+            ResultSet rs = stmt.executeQuery("select uids from t_bitmap");
+            while (rs.next()) {
+                byte[] bytes = rs.getBytes(1);
+
+                RoaringBitmap bitmap32 = new RoaringBitmap();
+                // Only Roaring64NavigableMap can work, Roaring64Bitmap can't work!!!
+                Roaring64NavigableMap bitmap64 = new Roaring64NavigableMap();
+                switch (bytes[0]) {
+                    case 0: // for empty bitmap
+                        break;
+                    case 1: // for only 1 element in bitmap32
+                        bitmap32.add(ByteBuffer.wrap(bytes, 1, bytes.length - 1)
+                            .order(ByteOrder.LITTLE_ENDIAN)
+                            .getInt());
+                        break;
+                    case 2: // for more than 1 elements in bitmap32
+                        bitmap32.deserialize(ByteBuffer.wrap(bytes, 1, bytes.length - 1));
+                        break;
+                    case 3: // for only 1 element in bitmap64
+                        bitmap64.add(ByteBuffer.wrap(bytes, 1, bytes.length - 1)
+                            .order(ByteOrder.LITTLE_ENDIAN)
+                            .getLong());
+                        break;
+                    case 4: // for more than 1 elements in bitmap64
+                        Object[] tuple2 = decodeVarint64(bytes);
+                        int offset = (int) tuple2[1];
+                        int newLen = 8 + bytes.length - offset;
+
+                        try (ByteArrayOutputStream baos = new ByteArrayOutputStream(newLen);
+                             DataOutputStream dos = new DataOutputStream(baos)) {
+                            dos.write((byte[]) tuple2[0]);
+                            dos.write(bytes, offset, bytes.length - offset);
+                            dos.flush();
+                            try (DataInputStream dis = new DataInputStream(
+                                new ByteArrayInputStream(baos.toByteArray()))) {
+                                bitmap64.deserializePortable(dis);
+                            }
+                        }
+                        break;
+                }
+                System.out.println(bytes[0] <= 2 ? bitmap32 : bitmap64);
+            }
+        }
+    }
+
+    static Object[] decodeVarint64(byte[] bt) { // nolint
+        long result = 0;
+        int shift = 0;
+        short B = 128;
+        int idx = 1;
+        for (; ; ) {
+            short readByte = bt[idx];
+            idx++;
+            boolean isEnd = (readByte & B) == 0;
+            result |= (long) (readByte & (B - 1)) << (shift * 7);
+            if (isEnd) {
+                break;
+            }
+            shift++;
+        }
+        byte[] bytes = new byte[8];
+        for (int i = 0; i < bytes.length; i++) {
+            // LITTLE_ENDIAN
+            bytes[i] = (byte) (result >> 8 * i);
+        }
+        return new Object[]{bytes, idx};
+    }
+}