[Enhancement](Nerieds) add switch for developing Nereids DML (#20100)

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

@@ -72,6 +72,14 @@ public class InsertIntoTableCommand extends Command implements ForwardWithSync {
 
     @Override
     public void run(ConnectContext ctx, StmtExecutor executor) throws Exception {
+        if (!ctx.getSessionVariable().isEnableNereidsDML()) {
+            try {
+                ctx.getSessionVariable().enableFallbackToOriginalPlannerOnce();
+            } catch (Exception e) {
+                throw new AnalysisException("failed to set fallback to original planner to true", e);
+            }
+            throw new AnalysisException("Nereids DML is disabled, will try to fall back to the original planner");
+        }
         if (ctx.isTxnModel()) {
             // in original planner, if is in txn model, insert into select command and tableRef >= 1 will be refused.
             // we can just run select a one-row-relation like select 1, 2, 3

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

@@ -171,6 +171,8 @@ public class SessionVariable implements Serializable, Writable {
     // turn off all automatic join reorder algorithms
     public static final String DISABLE_JOIN_REORDER = "disable_join_reorder";
 
+    public static final String ENABLE_NEREIDS_DML = "enable_nereids_dml";
+
     public static final String ENABLE_BUSHY_TREE = "enable_bushy_tree";
 
     public static final String ENABLE_PARTITION_TOPN = "enable_partition_topn";
@@ -572,6 +574,9 @@ public class SessionVariable implements Serializable, Writable {
     @VariableMgr.VarAttr(name = EXTRACT_WIDE_RANGE_EXPR, needForward = true)
     public boolean extractWideRangeExpr = true;
 
+    @VariableMgr.VarAttr(name = ENABLE_NEREIDS_DML)
+    public boolean enableNereidsDML = false;
+
     @VariableMgr.VarAttr(name = ENABLE_VECTORIZED_ENGINE, expType = ExperimentalType.EXPERIMENTAL_ONLINE)
     public boolean enableVectorizedEngine = true;
 
@@ -1284,6 +1289,10 @@ public class SessionVariable implements Serializable, Writable {
         return enableFoldConstantByBe;
     }
 
+    public boolean isEnableNereidsDML() {
+        return enableNereidsDML;
+    }
+
     public void setEnableFoldConstantByBe(boolean foldConstantByBe) {
         this.enableFoldConstantByBe = foldConstantByBe;
     }

regression-test/suites/nereids_p0/insert_into_table/unsupport_type.groovy

@@ -23,7 +23,8 @@ suite("nereids_insert_array_type") {
 
     test {
         sql 'insert into arr_t select id, kaint from src'
-        exception 'type ARRAY<INT> is unsupported for Nereids'
+        // exception 'type ARRAY<INT> is unsupported for Nereids'
+        exception null
     }
 
     sql 'set enable_fallback_to_original_planner=true'