[enhance](auto-partition) forbid null column for auto partition (#29749)

fe/fe-core/src/main/java/org/apache/doris/analysis/PartitionDesc.java

@@ -190,9 +190,14 @@ public class PartitionDesc {
                         throw new AnalysisException("Complex type column can't be partition column: "
                                 + columnDef.getType().toString());
                     }
+                    // prohibit to create auto partition with null column anyhow
+                    if (this.isAutoCreatePartitions && columnDef.isAllowNull()) {
+                        throw new AnalysisException("The auto partition column must be NOT NULL");
+                    }
                     if (!ConnectContext.get().getSessionVariable().isAllowPartitionColumnNullable()
                             && columnDef.isAllowNull()) {
-                        throw new AnalysisException("The partition column must be NOT NULL");
+                        throw new AnalysisException(
+                                "The partition column must be NOT NULL with allow_partition_column_nullable OFF");
                     }
                     if (this instanceof ListPartitionDesc && columnDef.isAllowNull()) {
                         throw new AnalysisException("The list partition column must be NOT NULL");

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/info/CreateTableInfo.java

@@ -138,6 +138,7 @@ public class CreateTableInfo {
         this.autoPartitionExprs = autoPartitionExprs;
         this.partitionType = partitionType;
         this.partitionColumns = partitionColumns;
+        appendColumnFromExprs();
         this.partitions = partitions;
         this.distribution = distribution;
         this.rollups = Utils.copyRequiredList(rollups);
@@ -173,6 +174,7 @@ public class CreateTableInfo {
         this.autoPartitionExprs = autoPartitionExprs;
         this.partitionType = partitionType;
         this.partitionColumns = partitionColumns;
+        appendColumnFromExprs();
         this.partitions = partitions;
         this.distribution = distribution;
         this.rollups = Utils.copyRequiredList(rollups);
@@ -650,8 +652,13 @@ public class CreateTableInfo {
             throw new AnalysisException("Complex type column can't be partition column: "
                     + column.getType().toString());
         }
+        // prohibit to create auto partition with null column anyhow
+        if (this.isAutoPartition && column.isNullable()) {
+            throw new AnalysisException("The auto partition column must be NOT NULL");
+        }
         if (!ctx.getSessionVariable().isAllowPartitionColumnNullable() && column.isNullable()) {
-            throw new AnalysisException("The partition column must be NOT NULL");
+            throw new AnalysisException(
+                    "The partition column must be NOT NULL with allow_partition_column_nullable OFF");
         }
         if (partitionType.equalsIgnoreCase(PartitionType.LIST.name()) && column.isNullable()) {
             throw new AnalysisException("The list partition column must be NOT NULL");
@@ -882,4 +889,14 @@ public class CreateTableInfo {
             }
         }).collect(Collectors.toList());
     }
+
+    private void appendColumnFromExprs() {
+        for (Expression autoExpr : autoPartitionExprs) {
+            for (Expression child : autoExpr.children()) {
+                if (child instanceof UnboundSlot) {
+                    partitionColumns.add(((UnboundSlot) child).getName());
+                }
+            }
+        }
+    }
 }

fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java

@@ -767,7 +767,11 @@ public class SessionVariable implements Serializable, Writable {
     @VariableMgr.VarAttr(name = SHOW_HIDDEN_COLUMNS, flag = VariableMgr.SESSION_ONLY)
     public boolean showHiddenColumns = false;
 
-    @VariableMgr.VarAttr(name = ALLOW_PARTITION_COLUMN_NULLABLE)
+    @VariableMgr.VarAttr(name = ALLOW_PARTITION_COLUMN_NULLABLE, description = {
+            "是否允许 NULLABLE 列作为 PARTITION 列。开启后，RANGE PARTITION 允许 NULLABLE PARTITION 列"
+                    + "（LIST PARTITION当前不支持）。默认开。",
+            "Whether to allow NULLABLE columns as PARTITION columns. When ON, RANGE PARTITION allows "
+                    + "NULLABLE PARTITION columns (LIST PARTITION is not supported currently). ON by default." })
     public boolean allowPartitionColumnNullable = true;
 
     @VariableMgr.VarAttr(name = DELETE_WITHOUT_PARTITION, needForward = true)

fe/fe-core/src/test/java/org/apache/doris/analysis/RangePartitionPruneTest.java

@@ -105,7 +105,7 @@ public class RangePartitionPruneTest extends PartitionPruneTestBase {
                         + "PROPERTIES ('replication_num' = '1');";
 
         String autoCreatePartitionTable = new String("CREATE TABLE test.test_to_date_trunc(\n"
-                + "    event_day DATETIME\n"
+                + "    event_day DATETIME NOT NULL\n"
                 + ")\n"
                 + "DUPLICATE KEY(event_day)\n"
                 + "AUTO PARTITION BY range date_trunc(event_day, \"day\") (\n"

fe/fe-core/src/test/java/org/apache/doris/service/FrontendServiceImplTest.java

@@ -82,7 +82,7 @@ public class FrontendServiceImplTest {
     @Test
     public void testCreatePartitionRange() throws Exception {
         String createOlapTblStmt = new String("CREATE TABLE test.partition_range(\n"
-                + "    event_day DATETIME,\n"
+                + "    event_day DATETIME NOT NULL,\n"
                 + "    site_id INT DEFAULT '10',\n"
                 + "    city_code VARCHAR(100)\n"
                 + ")\n"
@@ -123,7 +123,7 @@ public class FrontendServiceImplTest {
         String createOlapTblStmt = new String("CREATE TABLE test.partition_list(\n"
                 + "    event_day DATETIME,\n"
                 + "    site_id INT DEFAULT '10',\n"
-                + "    city_code VARCHAR(100) not null\n"
+                + "    city_code VARCHAR(100) NOT NULL\n"
                 + ")\n"
                 + "DUPLICATE KEY(event_day, site_id, city_code)\n"
                 + "AUTO PARTITION BY list (city_code) (\n"