[fix](variant) building index on the variant column is prohibited (#49159)

Index files are not created for variant columns during the build index
process, causing link file operations to fail

Author: csun5285

fe/fe-core/src/main/java/org/apache/doris/alter/SchemaChangeHandler.java

@@ -2117,6 +2117,19 @@ public int getAsInt() {
                                         + existedIdx.getIndexName() + " of type " + existedIdx.getIndexType()
                                         + " does not support lightweight index changes.");
                             }
+                            for (Column column : olapTable.getBaseSchema()) {
+                                if (!column.getType().isVariantType()) {
+                                    continue;
+                                }
+                                // variant type column can not support for building index
+                                for (String indexColumn : existedIdx.getColumns()) {
+                                    if (column.getName().equalsIgnoreCase(indexColumn)) {
+                                        throw new DdlException("BUILD INDEX operation failed: The "
+                                                + indexDef.getIndexName() + " index can not be built on the "
+                                                + indexColumn + " column, because it is a variant type column.");
+                                    }
+                                }
+                            }
                             index = existedIdx.clone();
                             if (indexDef.getPartitionNames().isEmpty()) {
                                 invertedIndexOnPartitions.put(index.getIndexId(), olapTable.getPartitionNames());

regression-test/suites/variant_p0/with_index/var_index.groovy

@@ -106,4 +106,29 @@ suite("regression_test_variant_var_index", "p0, nonConcurrent"){
     """
     sql """ALTER TABLE var_index ADD INDEX idx_var(v) USING INVERTED"""
     sql """ set disable_inverted_index_v1_for_variant = true """
+
+    try {
+        sql """ build index idx_var on var_index"""
+    } catch (Exception e) {
+        log.info(e.getMessage())
+        assertTrue(e.getMessage().contains("The idx_var index can not be built on the v column, because it is a variant type column"))
+    }
+
+    sql "DROP TABLE IF EXISTS var_index"
+    sql """
+        CREATE TABLE IF NOT EXISTS var_index (
+            k bigint,
+            v variant
+        )
+        DUPLICATE KEY(`k`)
+        DISTRIBUTED BY HASH(k) BUCKETS 1 
+        properties("replication_num" = "1", "disable_auto_compaction" = "true", "inverted_index_storage_format" = "V2");
+    """
+    sql """ALTER TABLE var_index ADD INDEX idx_var(v) USING INVERTED"""
+    try {
+        sql """ build index idx_var on var_index"""
+    } catch (Exception e) {
+        log.info(e.getMessage())
+        assertTrue(e.getMessage().contains("The idx_var index can not be built on the v column, because it is a variant type column"))
+    }
 }