apache · Yukang-Lian · Aug 27, 2026
@@ -70,6 +70,7 @@
 import org.apache.doris.common.UserException;
 import org.apache.doris.common.util.BufferSizeUtil;
 import org.apache.doris.common.util.DbUtil;
+import org.apache.doris.common.util.DebugPointUtil;
 import org.apache.doris.common.util.DynamicPartitionUtil;
 import org.apache.doris.common.util.ListComparator;
 import org.apache.doris.common.util.PropertyAnalyzer;
@@ -3731,18 +3732,27 @@ public void updateBaseIndexSchema(OlapTable olapTable, Map<Long, LinkedList<Colu
         for (int i = 0; i < indexIds.size(); i++) {
             List<Column> indexSchema = indexSchemaMap.get(indexIds.get(i));
             MaterializedIndexMeta currentIndexMeta = olapTable.getIndexMetaByIndexId(indexIds.get(i));
+            String forceStaleMaxColUniqueIdTable = DebugPointUtil.getDebugParamOrDefault(
+                    "FE.SchemaChangeHandler.updateBaseIndexSchema.forceStaleMaxColUniqueId", "table_name", "");
+            if (olapTable.getName().equals(forceStaleMaxColUniqueIdTable)) {
+                currentIndexMeta.setMaxColUniqueId(Column.COLUMN_UNIQUE_ID_INIT_VALUE);
+            }
+
+            // Preserve unique ids from the old schema before replacing it. Otherwise a stale maxColUniqueId can
+            // forget the highest id when its column is dropped, allowing a later column to reuse that id.
+            int maxColUniqueId = currentIndexMeta.getMaxColUniqueId();
+            for (Column column : currentIndexMeta.getSchema()) {
+                maxColUniqueId = Math.max(maxColUniqueId, column.getUniqueId());
+            }
             currentIndexMeta.setSchema(indexSchema);
 
             int currentSchemaVersion = currentIndexMeta.getSchemaVersion();
             int newSchemaVersion = currentSchemaVersion + 1;
             currentIndexMeta.setSchemaVersion(newSchemaVersion);
 
             //update max column unique id
-            int maxColUniqueId = currentIndexMeta.getMaxColUniqueId();
             for (Column column : indexSchema) {
-                if (column.getUniqueId() > maxColUniqueId) {
-                    maxColUniqueId = column.getUniqueId();
-                }
+                maxColUniqueId = Math.max(maxColUniqueId, column.getUniqueId());
             }
             currentIndexMeta.setMaxColUniqueId(maxColUniqueId);
             currentIndexMeta.setIndexes(indexes);

diff --git a/fe/fe-core/src/main/java/org/apache/doris/catalog/MaterializedIndexMeta.java b/fe/fe-core/src/main/java/org/apache/doris/catalog/MaterializedIndexMeta.java
@@ -279,6 +279,7 @@ public void gsonPostProcess() throws IOException {
         if (sessionVariables == null) {
             sessionVariables = Maps.newHashMap();
         }
+        refreshMaxColUniqueId();
         initColumnNameMap();
     }
 
@@ -349,7 +350,7 @@ public int incAndGetMaxColUniqueId() {
     }
 
     public int getMaxColUniqueId() {
-        return this.maxColUniqueId;
+        return Math.max(maxColUniqueId, getSchemaMaxColUniqueId());
     }
 
     public void setMaxColUniqueId(int maxColUniqueId) {
@@ -367,6 +368,18 @@ public void initSchemaColumnUniqueId() {
         });
     }
 
+    private void refreshMaxColUniqueId() {
+        maxColUniqueId = getMaxColUniqueId();
+    }
+
+    private int getSchemaMaxColUniqueId() {
+        int schemaMaxColUniqueId = Column.COLUMN_UNIQUE_ID_INIT_VALUE;
+        for (Column column : schema) {
+            schemaMaxColUniqueId = Math.max(schemaMaxColUniqueId, column.getUniqueId());
+        }
+        return schemaMaxColUniqueId;
+    }
+
     public void initColumnNameMap() {
         // case insensitive
         nameToColumn = Maps.newTreeMap(String.CASE_INSENSITIVE_ORDER);

@@ -844,6 +844,43 @@ public void testAggAddOrDropColumn() throws Exception {
         }
     }
 
+    @Test
+    public void testReaddDroppedValueColumnUsesNewUniqueId() throws Exception {
+        String tableName = "sc_dup_readd_value_column";
+        dropTable("test." + tableName, false);
+        createTable("CREATE TABLE test." + tableName + " (\n"
+                + "event_time DATETIME NOT NULL,\n"
+                + "user_id BIGINT NOT NULL,\n"
+                + "item_id INT NOT NULL,\n"
+                + "amount DECIMAL(10, 2) NOT NULL,\n"
+                + "city VARCHAR(64) NOT NULL\n"
+                + ") DUPLICATE KEY(event_time, user_id)\n"
+                + "DISTRIBUTED BY HASH(user_id) BUCKETS 1\n"
+                + "PROPERTIES ('replication_num' = '1', 'light_schema_change' = 'true')");
+
+        Database db = Env.getCurrentInternalCatalog().getDbOrMetaException("test");
+        OlapTable tbl = (OlapTable) db.getTableOrMetaException(tableName, Table.TableType.OLAP);
+        MaterializedIndexMeta indexMeta = tbl.getIndexMetaByIndexId(tbl.getBaseIndexId());
+        int droppedColumnUniqueId = tbl.getColumn("city").getUniqueId();
+
+        tbl.writeLock();
+        try {
+            indexMeta.setMaxColUniqueId(Column.COLUMN_UNIQUE_ID_INIT_VALUE);
+        } finally {
+            tbl.writeUnlock();
+        }
+
+        alterTable("ALTER TABLE test." + tableName + " DROP COLUMN city", connectContext);
+        jobSize++;
+        waitAlterJobDone(Env.getCurrentEnv().getSchemaChangeHandler().getAlterJobsV2());
+        Assertions.assertTrue(indexMeta.getMaxColUniqueId() >= droppedColumnUniqueId);
+
+        alterTable("ALTER TABLE test." + tableName + " ADD COLUMN city VARCHAR(64)", connectContext);
+        jobSize++;
+        waitAlterJobDone(Env.getCurrentEnv().getSchemaChangeHandler().getAlterJobsV2());
+        Assertions.assertTrue(tbl.getColumn("city").getUniqueId() > droppedColumnUniqueId);
+    }
+
     @Test
     public void testUniqAddOrDropColumn() throws Exception {
 

diff --git a/fe/fe-core/src/test/java/org/apache/doris/catalog/MaterializedIndexMetaTest.java b/fe/fe-core/src/test/java/org/apache/doris/catalog/MaterializedIndexMetaTest.java
@@ -0,0 +1,64 @@
+// 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.
+
+package org.apache.doris.catalog;
+
+import org.apache.doris.persist.gson.GsonUtils;
+import org.apache.doris.thrift.TStorageType;
+
+import com.google.common.collect.Lists;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class MaterializedIndexMetaTest {
+
+    @Test
+    public void testDeserializeRepairsStaleMaxColUniqueId() throws Exception {
+        MaterializedIndexMeta meta = createMeta();
+        meta.setMaxColUniqueId(Column.COLUMN_UNIQUE_ID_INIT_VALUE);
+
+        String json = GsonUtils.GSON.toJson(meta);
+        MaterializedIndexMeta replayedMeta = GsonUtils.GSON.fromJson(json, MaterializedIndexMeta.class);
+
+        Assertions.assertEquals(7, replayedMeta.getMaxColUniqueId());
+        replayedMeta.setSchema(Lists.newArrayList(replayedMeta.getSchema().get(0)));
+        Assertions.assertEquals(8, replayedMeta.incAndGetMaxColUniqueId());
+    }
+
+    @Test
+    public void testDeserializePreservesHigherMaxColUniqueId() throws Exception {
+        MaterializedIndexMeta meta = createMeta();
+        meta.setMaxColUniqueId(11);
+
+        String json = GsonUtils.GSON.toJson(meta);
+        MaterializedIndexMeta replayedMeta = GsonUtils.GSON.fromJson(json, MaterializedIndexMeta.class);
+
+        replayedMeta.setSchema(Lists.newArrayList(replayedMeta.getSchema().get(0)));
+        Assertions.assertEquals(11, replayedMeta.getMaxColUniqueId());
+        Assertions.assertEquals(12, replayedMeta.incAndGetMaxColUniqueId());
+    }
+
+    private MaterializedIndexMeta createMeta() {
+        Column keyColumn = new Column("k", PrimitiveType.INT);
+        keyColumn.setUniqueId(0);
+        Column valueColumn = new Column("v", PrimitiveType.INT);
+        valueColumn.setUniqueId(7);
+        return new MaterializedIndexMeta(
+                1L, Lists.newArrayList(keyColumn, valueColumn), 1, 1, (short) 1,
+                TStorageType.COLUMN, KeysType.DUP_KEYS, null);
+    }
+}
diff --git a/regression-test/data/fault_injection_p0/test_readd_dropped_column_unique_id.out b/regression-test/data/fault_injection_p0/test_readd_dropped_column_unique_id.out
@@ -0,0 +1,8 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !old_row --
+1	\N
+
+-- !all_rows --
+1	\N
+2	67890
+
diff --git a/regression-test/suites/fault_injection_p0/test_readd_dropped_column_unique_id.groovy b/regression-test/suites/fault_injection_p0/test_readd_dropped_column_unique_id.groovy
@@ -0,0 +1,67 @@
+// 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.apache.doris.regression.suite.ClusterOptions
+
+suite("test_readd_dropped_column_unique_id", "docker") {
+    def options = new ClusterOptions()
+    options.feConfigs += ["enable_debug_points=true"]
+    options.cloudMode = false
+
+    docker(options) {
+        sql "DROP TABLE IF EXISTS test_readd_dropped_column_unique_id"
+        sql """
+            CREATE TABLE test_readd_dropped_column_unique_id (
+                k INT NOT NULL,
+                v INT NULL
+            )
+            DUPLICATE KEY(k)
+            DISTRIBUTED BY HASH(k) BUCKETS 1
+            PROPERTIES (
+                "replication_num" = "1",
+                "light_schema_change" = "true",
+                "disable_auto_compaction" = "true"
+            )
+        """
+        sql "INSERT INTO test_readd_dropped_column_unique_id VALUES (1, 12345)"
+        sql "SYNC"
+
+        def debugPoint = "FE.SchemaChangeHandler.updateBaseIndexSchema.forceStaleMaxColUniqueId"
+        try {
+            GetDebugPoint().enableDebugPointForAllFEs(
+                    debugPoint, [table_name: "test_readd_dropped_column_unique_id"])
+            sql "ALTER TABLE test_readd_dropped_column_unique_id DROP COLUMN v"
+        } finally {
+            GetDebugPoint().disableDebugPointForAllFEs(debugPoint)
+        }
+
+        sql "ALTER TABLE test_readd_dropped_column_unique_id ADD COLUMN v INT NULL"
+
+        order_qt_old_row """
+            SELECT k, v
+            FROM test_readd_dropped_column_unique_id
+            ORDER BY k
+        """
+
+        sql "INSERT INTO test_readd_dropped_column_unique_id VALUES (2, 67890)"
+        order_qt_all_rows """
+            SELECT k, v
+            FROM test_readd_dropped_column_unique_id
+            ORDER BY k
+        """
+    }
+}