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From: amit <[email protected]>
Subject: [PATCH] Make partitioned tables play nicely with bulk-insert
Date: Mon, 23 Jan 2017 17:00:19 +0900

When COPY'ing (or bulk-inserting) into a partitioned table, the target
heap may change from one tuple to next.  We better ask ReadBufferBI()
to get a new buffer every time such change occurs.  We do that by
having CopyFrom() call the new ReleaseBulkInsertStatePin() which unpins
the BulkInsertState.cur_buffer and sets it to InvalidBuffer, which is
enough a signal for ReadBufferBI() to do the right thing.

This also fixes the bug that tuples ended up being inserted into the
wrong partition, which occurred exactly because the wrong buffer was
used.

Reported by: 高增琦, Venkata B Nagothi, Ragnar Ouchterlony
Patch by: Amit Langote (idea by Robert Haas)
Reports: https://www.postgresql.org/message-id/CAFmBtr32FDOqofo8yG-4mjzL1HnYHxXK5S9OGFJ%3D%3DcJpgEW4vA%40mail...
         https://www.postgresql.org/message-id/CAEyp7J9WiX0L3DoiNcRrY-9iyw%3DqP%2Bj%3DDLsAnNFF1xT2J1ggfQ%40ma...
         https://www.postgresql.org/message-id/16d73804-c9cd-14c5-463e-5caad563ff77%40agama.tv
---
 src/backend/access/heap/heapam.c | 11 +++++++++++
 src/backend/commands/copy.c      | 12 ++++++++++++
 src/include/access/heapam.h      |  1 +
 3 files changed, 24 insertions(+)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 1ce42ea970..5fd7f1e1a2 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -2324,6 +2324,17 @@ FreeBulkInsertState(BulkInsertState bistate)
 	pfree(bistate);
 }
 
+/*
+ * ReleaseBulkInsertStatePin - release a buffer currently held in bistate
+ */
+void
+ReleaseBulkInsertStatePin(BulkInsertState bistate)
+{
+	if (bistate->current_buf != InvalidBuffer)
+		ReleaseBuffer(bistate->current_buf);
+	bistate->current_buf = InvalidBuffer;
+}
+
 
 /*
  *	heap_insert		- insert tuple into a heap
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index c05e14e26f..86bd53c179 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -2307,6 +2307,7 @@ CopyFrom(CopyState cstate)
 	uint64		processed = 0;
 	bool		useHeapMultiInsert;
 	int			nBufferedTuples = 0;
+	int			prev_leaf_part_index = -1;
 
 #define MAX_BUFFERED_TUPLES 1000
 	HeapTuple  *bufferedTuples = NULL;	/* initialize to silence warning */
@@ -2562,6 +2563,17 @@ CopyFrom(CopyState cstate)
 				   leaf_part_index < cstate->num_partitions);
 
 			/*
+			 * If the current tuple is mapped to a partition that is not same
+			 * as the previous, we better make the BI (bulk-insert) mechanism
+			 * get a new buffer.
+			 */
+			if (prev_leaf_part_index != leaf_part_index)
+			{
+				ReleaseBulkInsertStatePin(bistate);
+				prev_leaf_part_index = leaf_part_index;
+			}
+
+			/*
 			 * Save the old ResultRelInfo and switch to the one corresponding
 			 * to the selected partition.
 			 */
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index ee7e05a3ec..a864f7860d 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -147,6 +147,7 @@ extern void setLastTid(const ItemPointer tid);
 
 extern BulkInsertState GetBulkInsertState(void);
 extern void FreeBulkInsertState(BulkInsertState);
+extern void ReleaseBulkInsertStatePin(BulkInsertState bistate);
 
 extern Oid heap_insert(Relation relation, HeapTuple tup, CommandId cid,
 			int options, BulkInsertState bistate);
-- 
2.11.0


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