From ccf8a84f785c96ac7ae01e17b4fb7999183fed9e Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Mon, 25 Mar 2019 13:29:34 -0300
Subject: [PATCH v6 1/3] implement heapscan_get_blocks_done

---
 src/backend/access/heap/heapam.c | 34 ++++++++++++++++++++++++++++++++
 src/include/access/heapam.h      |  1 +
 2 files changed, 35 insertions(+)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index fa747be73ab..a7f6c09dcd0 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -1053,6 +1053,40 @@ heapgettup_pagemode(HeapScanDesc scan,
 	}
 }
 
+/*
+ * Return the number of blocks that have been read by this scan since
+ * starting.  This is not 100% accurate, because in a parallel scan the
+ * counter can be moving concurrently.
+ */
+BlockNumber
+heapscan_get_blocks_done(TableScanDesc sscan)
+{
+	HeapScanDesc	hscan = (HeapScanDesc) sscan;
+	BlockNumber		startblock;
+	BlockNumber		blocks_done;
+
+	if (hscan->rs_base.rs_parallel != NULL)
+	{
+		ParallelBlockTableScanDesc bpscan;
+
+		bpscan = (ParallelBlockTableScanDesc) hscan->rs_base.rs_parallel;
+		startblock = bpscan->phs_startblock;
+	}
+	else
+		startblock = hscan->rs_startblock;
+
+	/*
+	 * Might have wrapped around the end of the relation, if startblock was
+	 * not zero.
+	 */
+	if (hscan->rs_cblock > startblock)
+		blocks_done = hscan->rs_cblock - startblock;
+	else
+		blocks_done = hscan->rs_nblocks - startblock +
+			hscan->rs_cblock;
+
+	return blocks_done;
+}
 
 #if defined(DISABLE_COMPLEX_MACRO)
 /*
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index e72f9787517..d4f537b3791 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -118,6 +118,7 @@ extern TableScanDesc heap_beginscan(Relation relation, Snapshot snapshot,
 extern void heap_setscanlimits(TableScanDesc scan, BlockNumber startBlk,
 				   BlockNumber endBlk);
 extern void heapgetpage(TableScanDesc scan, BlockNumber page);
+extern BlockNumber heapscan_get_blocks_done(TableScanDesc sscan);
 extern void heap_rescan(TableScanDesc scan, ScanKey key, bool set_params,
 			bool allow_strat, bool allow_sync, bool allow_pagemode);
 extern void heap_rescan_set_params(TableScanDesc scan, ScanKey key,
-- 
2.17.1