Add and use BitmapHeapScanDescData struct

Move the several members of HeapScanDescData which are specific to
Bitmap Heap Scans into a new struct, BitmapHeapScanDescData, which
inherits from HeapScanDescData.

This reduces the size of the HeapScanDescData for other types of scans
and will allow us to add additional bitmap heap scan-specific members in
the future without fear of bloating the HeapScanDescData.

Reviewed-by: Tomas Vondra
Discussion: https://postgr.es/m/c736f6aa-8b35-4e20-9621-62c7c82e2168%40vondra.me

1 files changed, 16 insertions, 8 deletions

diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 7d06dad83fc..1640d9c32f7 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -92,22 +92,30 @@ typedef struct HeapScanDescData
 	 */
 	ParallelBlockTableScanWorkerData *rs_parallelworkerdata;
 
+	/* these fields only used in page-at-a-time mode and for bitmap scans */
+	uint32		rs_cindex;		/* current tuple's index in vistuples */
+	uint32		rs_ntuples;		/* number of visible tuples on page */
+	OffsetNumber rs_vistuples[MaxHeapTuplesPerPage];	/* their offsets */
+}			HeapScanDescData;
+typedef struct HeapScanDescData *HeapScanDesc;
+
+typedef struct BitmapHeapScanDescData
+{
+	HeapScanDescData rs_heap_base;
+
 	/*
 	 * These fields are only used for bitmap scans for the "skip fetch"
 	 * optimization. Bitmap scans needing no fields from the heap may skip
 	 * fetching an all visible block, instead using the number of tuples per
 	 * block reported by the bitmap to determine how many NULL-filled tuples
-	 * to return.
+	 * to return. They are common to parallel and serial BitmapHeapScans
 	 */
+
+	/* page of VM containing info for current block */
 	Buffer		rs_vmbuffer;
 	int			rs_empty_tuples_pending;
-
-	/* these fields only used in page-at-a-time mode and for bitmap scans */
-	uint32		rs_cindex;		/* current tuple's index in vistuples */
-	uint32		rs_ntuples;		/* number of visible tuples on page */
-	OffsetNumber rs_vistuples[MaxHeapTuplesPerPage];	/* their offsets */
-}			HeapScanDescData;
-typedef struct HeapScanDescData *HeapScanDesc;
+}			BitmapHeapScanDescData;
+typedef struct BitmapHeapScanDescData *BitmapHeapScanDesc;
 
 /*
  * Descriptor for fetches from heap via an index.