.

src/backend/distributed/planner/distributed_planner.c

@@ -155,6 +155,15 @@ static bool CheckPostPlanDistribution(bool isDistributedQuery,
 									  List *rangeTableList,
 									  Query *plannedQuery);
 
+static Query *
+RewriteInsertSelectForPartialNextval(Query *originalQuery);
+static List *
+TargetEntryList(List *expressionList);
+static int
+FindRTEIndexInQuery(Query *query, RangeTblEntry *rte);
+RangeTblEntry *
+ExtractResultRelationRTEOrNull(Query *query);
+
 /* Distributed planner hook */
 PlannedStmt *
 distributed_planner(Query *parse,
@@ -848,6 +857,12 @@ InlineCtesAndCreateDistributedPlannedStmt(uint64 planId,
 	/* after inlining, we shouldn't have any inlinable CTEs */
 	Assert(!QueryTreeContainsInlinableCTE(copyOfOriginalQuery));
 
+	// if (QueryContainsNextval(copyOfOriginalQuery))
+	// {
+	// 	/* rewrite the query to partial pushdown form */
+	// 	copyOfOriginalQuery = RewriteInsertSelectForPartialNextval(copyOfOriginalQuery);
+	// }
+
 	/* simply recurse into CreateDistributedPlannedStmt() in a PG_TRY() block */
 	PlannedStmt *result = TryCreateDistributedPlannedStmt(planContext->plan,
 														  copyOfOriginalQuery,
@@ -860,6 +875,214 @@ InlineCtesAndCreateDistributedPlannedStmt(uint64 planId,
 }
 
 
+/*
+ * RewriteInsertSelectForPartialNextval
+ *
+ * Given an INSERT ... SELECT query that contains nextval() in its target list,
+ * rewrite the query so that the inner subquery (which is pushed down to workers)
+ * returns only the non-volatile (non-nextval) columns. The outer query then
+ * adds the nextval() calls in its target list. This forces nextval() to be
+ * evaluated on the coordinator.
+ *
+ * For example, this transforms:
+ *
+ *   INSERT INTO target (col1, col2, col3)
+ *   SELECT col1, nextval('seq'), col3
+ *   FROM distributed_table;
+ *
+ * into a plan roughly equivalent to:
+ *
+ *   INSERT INTO target (col1, col2, col3)
+ *   SELECT worker.col1, nextval('seq'), worker.col3
+ *   FROM (
+ *     SELECT col1, col3
+ *     FROM distributed_table
+ *   ) AS worker;
+ */
+Query *
+RewriteInsertSelectForPartialNextval(Query *originalQuery)
+{
+    /* 0) Basic check: should be an INSERT...SELECT query */
+    RangeTblEntry *insertRte = ExtractResultRelationRTEOrNull(originalQuery);
+    if (insertRte == NULL)
+    {
+        /* not an INSERT...SELECT, or no result table => skip rewriting */
+        return originalQuery;
+    }
+
+    /* 1) Get the result relation and the SELECT side RTE */
+    // RangeTblEntry *insertRte = ExtractResultRelationRTEOrError(originalQuery);
+    RangeTblEntry *selectRte = ExtractSelectRangeTableEntry(originalQuery);
+
+    /* 2) Ensure the SELECT side is an RTE_SUBQUERY. If not, wrap it. */
+    if (selectRte->rtekind != RTE_SUBQUERY)
+    {
+        Query *fakeSelect = makeNode(Query);
+        fakeSelect->commandType = CMD_SELECT;
+        fakeSelect->targetList = copyObject(selectRte->subquery->targetList);
+        /* Additional fields (rtable, jointree) should be copied as needed */
+        selectRte->rtekind = RTE_SUBQUERY;
+        selectRte->subquery = fakeSelect;
+    }
+
+    /* Optionally, wrap the subquery to get a clean target list */
+    selectRte->subquery = WrapSubquery(selectRte->subquery);
+    Query *subquery = selectRte->subquery;  /* This is now our inner subquery */
+
+    /*
+     * 3) Partition the subquery’s target list into:
+     *    - workerExprs: expressions that do NOT contain nextval()
+     *    - volatileExprs: expressions that DO contain nextval()
+     *
+     * We'll use a helper function RemoveNextvalFromTargetList() that,
+     * for each TargetEntry in subquery->targetList, places its expr into one of
+     * two lists depending on whether contain_nextval_expression_walker() returns true.
+     */
+    List *workerExprs = NIL;
+    List *volatileExprs = NIL;
+    ListCell *lc;
+    foreach(lc, subquery->targetList)
+    {
+        TargetEntry *tle = (TargetEntry *) lfirst(lc);
+        if (contain_nextval_expression_walker((Node *) tle->expr, NULL))
+            volatileExprs = lappend(volatileExprs, tle->expr);
+        else
+            workerExprs = lappend(workerExprs, tle->expr);
+    }
+
+    /*
+     * 4) Build new target lists:
+     *
+     * For the inner subquery: Use only the worker expressions.
+     * For the outer (coordinator) query: Build a target list that combines:
+     *    - Vars that reference the worker subquery’s output columns (for each workerExpr)
+     *    - The volatile expressions (e.g. nextval()) placed in their proper positions.
+     *
+     * Here we assume that the original target list order is preserved:
+     * e.g. if the original target list was:
+     *    [ expr1, expr2 (volatile), expr3 ]
+     * then the new outer target list should be:
+     *    [ Var(worker_col1), expr2, Var(worker_col2) ]
+     *
+     * This example assumes that the order of workerExprs and volatileExprs
+     * correspond to their positions in the original target list.
+     *
+     * A more robust implementation would walk the original target list and, for
+     * each entry, either replace it with a Var reference (if non-volatile) or
+     * keep the volatile expression.
+     */
+
+    /* Create new inner subquery target list from workerExprs */
+    List *newWorkerTList = TargetEntryList(workerExprs);
+    subquery->targetList = newWorkerTList;  /* inner subquery returns only worker columns */
+
+    /* Build the outer target list */
+    List *newOuterTList = NIL;
+    int outerResno = 1;
+    int workerIndex = 1;
+    int volatileIndex = 1;
+    /* For each original target entry, check if it was volatile or not.
+       For simplicity, we assume the original order is preserved in the concatenated lists.
+       A robust solution would store position info. */
+    foreach(lc, originalQuery->targetList)
+    {
+        TargetEntry *origTle = (TargetEntry *) lfirst(lc);
+        if (contain_nextval_expression_walker((Node *) origTle->expr, NULL))
+        {
+            /* Keep the volatile expression as is. */
+            TargetEntry *newTle = makeTargetEntry(copyObject(origTle->expr),
+                                                    outerResno,
+                                                    pstrdup(origTle->resname),
+                                                    false);
+            newOuterTList = lappend(newOuterTList, newTle);
+            volatileIndex++;
+        }
+        else
+        {
+            /* Replace non-volatile expression with a Var reference to the subquery's output.
+               We need to get the RTE index of the subquery.
+            */
+			int subqueryIndex = FindRTEIndexInQuery(originalQuery, selectRte);
+			TargetEntry *workerTle = (TargetEntry *) list_nth(newWorkerTList, workerIndex - 1);
+			Var *v = makeVar(subqueryIndex,           /* the RTE index (1-based) */
+							workerIndex,             /* attribute number within subquery TList */
+							exprType((Node *) workerTle->expr),
+							exprTypmod((Node *) workerTle->expr),
+							exprCollation((Node *) workerTle->expr),
+							0);
+			TargetEntry *newTle = makeTargetEntry((Expr *) v,
+												outerResno,
+												pstrdup(origTle->resname),
+												false);
+			newOuterTList = lappend(newOuterTList, newTle);
+			workerIndex++;
+        }
+        outerResno++;
+    }
+    originalQuery->targetList = newOuterTList;
+
+    /* Optionally, re-run any target list reordering to align with the physical table's column order */
+    ReorderInsertSelectTargetLists(originalQuery, insertRte, selectRte);
+
+    return originalQuery;
+}
+
+
+RangeTblEntry *
+ExtractResultRelationRTEOrNull(Query *query)
+{
+    if (query->resultRelation == 0)
+        return NULL;
+
+    RangeTblEntry *rte = rt_fetch(query->resultRelation, query->rtable);
+    return rte;
+}
+
+
+/*
+ * TargetEntryList creates a new target list from a list of expressions.
+ * Each expression is wrapped in a TargetEntry with an automatically generated
+ * column name.
+ */
+static List *
+TargetEntryList(List *expressionList)
+{
+    List *tlist = NIL;
+    ListCell *cell;
+    int colIndex = 1;
+
+    foreach(cell, expressionList)
+    {
+        Expr *expr = (Expr *) lfirst(cell);
+        StringInfo colName = makeStringInfo();
+        appendStringInfo(colName, "worker_col%d", colIndex);
+        TargetEntry *tle = makeTargetEntry(expr, colIndex, pstrdup(colName->data), false);
+        tlist = lappend(tlist, tle);
+        colIndex++;
+    }
+    return tlist;
+}
+
+/*
+ * FindRTEIndexInQuery returns the 1-based index of the given RTE in query->rtable.
+ * If not found, returns 0.
+ */
+static int
+FindRTEIndexInQuery(Query *query, RangeTblEntry *rte)
+{
+    ListCell *cell;
+    int index = 0;
+    foreach(cell, query->rtable)
+    {
+        index++;
+        if (lfirst(cell) == (void *) rte)
+            return index;
+    }
+    return 0;
+}
+
+
+
 /*
  * TryCreateDistributedPlannedStmt is a wrapper around CreateDistributedPlannedStmt, simply
  * calling it in PG_TRY()/PG_CATCH() block. The function returns a PlannedStmt if the input
@@ -1003,6 +1226,14 @@ CreateDistributedPlan(uint64 planId, bool allowRecursivePlanning, Query *origina
 
 		case INSERT_SELECT_INTO_LOCAL_TABLE:
 		{
+				
+			if (QueryContainsNextval(originalQuery))
+			{
+				/* rewrite the query to partial pushdown form */
+				originalQuery = RewriteInsertSelectForPartialNextval(originalQuery);
+			}
+
+
 			distributedPlan =
 				CreateInsertSelectIntoLocalTablePlan(planId,
 													 originalQuery,

src/backend/distributed/planner/insert_select_planner.c

@@ -310,11 +310,11 @@ CreateDistributedInsertSelectPlan(Query *originalQuery,
 
 	distributedPlan->modLevel = RowModifyLevelForQuery(originalQuery);
 
-	if (QueryContainsNextval(originalQuery))
+	// if (QueryContainsNextval(originalQuery))
-	{
+	// {
-		/* rewrite the query to partial pushdown form */
+	// 	/* rewrite the query to partial pushdown form */
-		originalQuery = RewriteInsertSelectForPartialNextval(originalQuery);
+	// 	originalQuery = RewriteInsertSelectForPartialNextval(originalQuery);
-	}
+	// }
 	
 	/*
 	 * Error semantics for INSERT ... SELECT queries are different than regular