[fix](variant) Fix metadata compatibility for FE

fe/fe-common/src/main/java/org/apache/doris/catalog/ScalarType.java

@@ -1221,4 +1221,18 @@ public int hashCode() {
         result = 31 * result + scale;
         return result;
     }
+
+    public int getVariantMaxSubcolumnsCount() {
+        if (this instanceof VariantType) {
+            return ((VariantType) this).getVariantMaxSubcolumnsCount();
+        }
+        return 0;
+    }
+
+    public boolean getVariantEnableTypedPathsToSparse() {
+        if (this instanceof VariantType) {
+            return ((VariantType) this).getEnableTypedPathsToSparse();
+        }
+        return false;
+    }
 }

fe/fe-common/src/main/java/org/apache/doris/catalog/VariantField.java

@@ -67,15 +67,15 @@ public TPatternType getPatternType() {
     }
 
     public String toSql(int depth) {
-        String typeSql;
-        if (depth < Type.MAX_NESTING_DEPTH) {
-            typeSql = type.toSql(depth + 1);
-        } else {
-            typeSql = "...";
+        StringBuilder sb = new StringBuilder();
+        if (patternType == TPatternType.MATCH_NAME) {
+            sb.append(patternType.toString()).append(" ");
         }
-        StringBuilder sb = new StringBuilder(patternType.toString() + " '");
-        if (type != null) {
-            sb.append(pattern).append("':").append(typeSql);
+
+        sb.append("'").append(pattern).append("'");
+        sb.append(":").append(type.toSql(depth + 1));
+        if (!comment.isEmpty()) {
+            sb.append(" COMMENT '").append(comment).append("'");
         }
         return sb.toString();
     }

fe/fe-core/src/main/java/org/apache/doris/catalog/Column.java

@@ -350,7 +350,7 @@ public void createChildrenColumn(Type type, Column column) {
                 c.setIsAllowNull(field.getContainsNull());
                 column.addChildrenColumn(c);
             }
-        } else if (type.isVariantType()) {
+        } else if (type.isVariantType() && type instanceof VariantType) {
             // variant may contain predefined structured fields
             ArrayList<VariantField> fields = ((VariantType) type).getPredefinedFields();
             for (VariantField field : fields) {
@@ -520,11 +520,11 @@ public int getScale() {
     }
 
     public int getVariantMaxSubcolumnsCount() {
-        return type.isVariantType() ? ((VariantType) type).getVariantMaxSubcolumnsCount() : -1;
+        return type.isVariantType() ? ((ScalarType) type).getVariantMaxSubcolumnsCount() : -1;
     }
 
     public boolean getVariantEnableTypedPathsToSparse() {
-        return type.isVariantType() ? ((VariantType) type).getEnableTypedPathsToSparse() : false;
+        return type.isVariantType() ? ((ScalarType) type).getVariantEnableTypedPathsToSparse() : false;
     }
 
     public AggregateType getAggregationType() {
@@ -890,8 +890,7 @@ public OlapFile.ColumnPB toPb(Set<String> bfColumns, List<Index> indexes) throws
                 builder.addChildrenColumns(c.toPb(Sets.newHashSet(), Lists.newArrayList()));
             }
         } else if (this.type.isVariantType()) {
-            VariantType variantType = (VariantType) this.getType();
-            builder.setVariantMaxSubcolumnsCount(variantType.getVariantMaxSubcolumnsCount());
+            builder.setVariantMaxSubcolumnsCount(this.getVariantMaxSubcolumnsCount());
             builder.setVariantEnableTypedPathsToSparse(this.getVariantEnableTypedPathsToSparse());
             // variant may contain predefined structured fields
             addChildren(builder);

fe/fe-core/src/main/java/org/apache/doris/nereids/types/VariantField.java

@@ -72,9 +72,22 @@ public org.apache.doris.catalog.VariantField toCatalogDataType() {
                 pattern, dataType.toCatalogDataType(), comment, patternType);
     }
 
+    /**
+     * Convert this VariantField to SQL string representation.
+     * @return SQL string representation of this VariantField
+     */
     public String toSql() {
-        return pattern + ":" + dataType.toSql()
-                + (comment.isEmpty() ? "" : " COMMENT " + comment);
+        StringBuilder sb = new StringBuilder();
+        if (patternType == TPatternType.MATCH_NAME) {
+            sb.append(patternType.toString()).append(" ");
+        }
+
+        sb.append("'").append(pattern).append("'");
+        sb.append(":").append(dataType.toSql());
+        if (!comment.isEmpty()) {
+            sb.append(" COMMENT '").append(comment).append("'");
+        }
+        return sb.toString();
     }
 
     public VariantField conversion() {

fe/fe-core/src/test/java/org/apache/doris/persist/ScalarTypeTest.java

@@ -0,0 +1,40 @@
+// 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.persist;
+
+import org.apache.doris.catalog.PrimitiveType;
+import org.apache.doris.catalog.ScalarType;
+import org.apache.doris.catalog.VariantType;
+import org.apache.doris.persist.gson.GsonUtils;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ScalarTypeTest {
+    @Test
+    public void testScalarType() {
+        ScalarType scalarType = new ScalarType(PrimitiveType.VARIANT);
+        String json = GsonUtils.GSON.toJson(scalarType);
+        System.out.println(json);
+        ScalarType scalarType2 = GsonUtils.GSON.fromJson(json, ScalarType.class);
+        Assert.assertFalse(scalarType2 instanceof VariantType);
+        Assert.assertEquals(scalarType.getPrimitiveType(), scalarType2.getPrimitiveType());
+        Assert.assertEquals(scalarType.getVariantMaxSubcolumnsCount(), 0);
+        Assert.assertEquals(scalarType.getVariantEnableTypedPathsToSparse(), false);
+    }
+}

regression-test/data/variant_p0/predefine/sql/q01.out

@@ -4,7 +4,7 @@
 
 -- !q01_2 --
 id	bigint	No	true	\N	
-v1	variant<MATCH_NAME_GLOB 'array_int':array<int>,MATCH_NAME_GLOB 'array_string':array<text>,MATCH_NAME_GLOB 'array_decimal':array<decimalv3(26,9)>,MATCH_NAME_GLOB 'array_datetime':array<datetimev2(0)>,MATCH_NAME_GLOB 'array_datetimev2':array<datetimev2(0)>,MATCH_NAME_GLOB 'array_date':array<datev2>,MATCH_NAME_GLOB 'array_datev2':array<datev2>,MATCH_NAME_GLOB 'array_ipv4':array<ipv4>,MATCH_NAME_GLOB 'array_ipv6':array<ipv6>,MATCH_NAME_GLOB 'array_float':array<float>,MATCH_NAME_GLOB 'array_boolean':array<boolean>,MATCH_NAME_GLOB 'int_':int,MATCH_NAME_GLOB 'string_':text,MATCH_NAME_GLOB 'decimal_':decimalv3(26,9),MATCH_NAME_GLOB 'datetime_':datetimev2(0),MATCH_NAME_GLOB 'datetimev2_':datetimev2(6),MATCH_NAME_GLOB 'date_':datev2,MATCH_NAME_GLOB 'datev2_':datev2,MATCH_NAME_GLOB 'ipv4_':ipv4,MATCH_NAME_GLOB 'ipv6_':ipv6,MATCH_NAME_GLOB 'float_':float,MATCH_NAME_GLOB 'boolean_':boolean,MATCH_NAME_GLOB 'varchar_':text,PROPERTIES ("variant_max_subcolumns_count" = "6")>	Yes	false	\N	NONE
+v1	variant<'array_int':array<int>,'array_string':array<text>,'array_decimal':array<decimalv3(26,9)>,'array_datetime':array<datetimev2(0)>,'array_datetimev2':array<datetimev2(0)>,'array_date':array<datev2>,'array_datev2':array<datev2>,'array_ipv4':array<ipv4>,'array_ipv6':array<ipv6>,'array_float':array<float>,'array_boolean':array<boolean>,'int_':int,'string_':text,'decimal_':decimalv3(26,9),'datetime_':datetimev2(0),'datetimev2_':datetimev2(6),'date_':datev2,'datev2_':datev2,'ipv4_':ipv4,'ipv6_':ipv6,'float_':float,'boolean_':boolean,'varchar_':text,PROPERTIES ("variant_max_subcolumns_count" = "6")>	Yes	false	\N	NONE
 v1.array_boolean	array<boolean>	Yes	false	\N	NONE
 v1.array_date	array<date>	Yes	false	\N	NONE
 v1.array_datetime	array<datetime>	Yes	false	\N	NONE