my-ship-it commented on code in PR #1398:
URL: https://github.com/apache/cloudberry/pull/1398#discussion_r2447332155
##########
src/backend/gpopt/translate/CTranslatorDXLToPlStmt.cpp:
##########
@@ -7282,4 +7425,75 @@ CTranslatorDXLToPlStmt::IsIndexForOrderBy(
}
return false;
}
+
+//---------------------------------------------------------------------------
+// @function:
+// CTranslatorDXLToPlStmt::ExtractParallelWorkersFromDXL
+//
+// @doc:
+// Extract parallel workers count from DXL node tree recursively.
+// Since parallel degree is uniform across all parallel scans in a
query,
+// returns the first parallel degree found from any
CDXLPhysicalParallelTableScan,
+// or 1 if no parallel scan exists.
+//
+//---------------------------------------------------------------------------
+ULONG
+CTranslatorDXLToPlStmt::ExtractParallelWorkersFromDXL(const CDXLNode *dxlnode)
+{
+ if (nullptr == dxlnode)
+ {
+ return 1;
+ }
+
+ CDXLOperator *dxlop = dxlnode->GetOperator();
+ if (EdxlopPhysicalParallelTableScan == dxlop->GetDXLOperator())
+ {
+ // Return parallel workers from the parallel table scan operator
+ // All parallel scans in the query share the same parallel
degree
+ CDXLPhysicalParallelTableScan *parallel_scan_dxlop =
+ CDXLPhysicalParallelTableScan::Cast(dxlop);
+ return parallel_scan_dxlop->UlParallelWorkers();
+ }
+ else if (EdxlopPhysicalTableScan == dxlop->GetDXLOperator() ||
+ EdxlopPhysicalDynamicTableScan ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalIndexScan == dxlop->GetDXLOperator() ||
+ EdxlopPhysicalIndexOnlyScan == dxlop->GetDXLOperator()
||
+ EdxlopPhysicalBitmapTableScan ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalDynamicBitmapTableScan ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalForeignScan == dxlop->GetDXLOperator() ||
+ EdxlopPhysicalDynamicForeignScan ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalDynamicIndexScan ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalDynamicIndexOnlyScan ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalValuesScan == dxlop->GetDXLOperator())
+ {
+ // Non-parallel scans (table, index, bitmap, foreign, values)
+ // These are leaf nodes in terms of parallel worker extraction
+ // Return 1 to indicate no parallel workers
+ return 1;
+ }
+ else if (EdxlopPhysicalMotionGather == dxlop->GetDXLOperator() ||
+ EdxlopPhysicalMotionBroadcast ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalMotionRedistribute ==
dxlop->GetDXLOperator() ||
+ EdxlopPhysicalMotionRandom == dxlop->GetDXLOperator()
||
+ EdxlopPhysicalMotionRoutedDistribute ==
dxlop->GetDXLOperator())
+ {
+ // Motion node creates a slice boundary - do not recurse into
child
+ // The child's parallel workers belong to the sending slice,
not receiving slice
+ // Return 0 to indicate the receiving slice (current slice) has
no parallel workers
+ return 1;
+ }
+
+ // Recursively check child nodes, return early when first parallel scan
is found
+ for (ULONG ul = 0; ul < dxlnode->Arity(); ul++)
+ {
+ ULONG child_parallel_workers =
ExtractParallelWorkersFromDXL((*dxlnode)[ul]);
Review Comment:
For HashJoin, should we return 3 or 6?
```
HashJoin
|─ Motion
|─ Parallel Scan on A (parallel_workers = 3)
|─ Motion
|─ Parallel Scan on B (parallel_workers = 6)
```
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