Add support for INSERT ... ON CONFLICT DO NOTHING/UPDATE.

The newly added ON CONFLICT clause allows to specify an alternative to
raising a unique or exclusion constraint violation error when inserting.
ON CONFLICT refers to constraints that can either be specified using a
inference clause (by specifying the columns of a unique constraint) or
by naming a unique or exclusion constraint.  DO NOTHING avoids the
constraint violation, without touching the pre-existing row.  DO UPDATE
SET ... [WHERE ...] updates the pre-existing tuple, and has access to
both the tuple proposed for insertion and the existing tuple; the
optional WHERE clause can be used to prevent an update from being
executed.  The UPDATE SET and WHERE clauses have access to the tuple
proposed for insertion using the "magic" EXCLUDED alias, and to the
pre-existing tuple using the table name or its alias.

This feature is often referred to as upsert.

This is implemented using a new infrastructure called "speculative
insertion". It is an optimistic variant of regular insertion that first
does a pre-check for existing tuples and then attempts an insert.  If a
violating tuple was inserted concurrently, the speculatively inserted
tuple is deleted and a new attempt is made.  If the pre-check finds a
matching tuple the alternative DO NOTHING or DO UPDATE action is taken.
If the insertion succeeds without detecting a conflict, the tuple is
deemed inserted.

To handle the possible ambiguity between the excluded alias and a table
named excluded, and for convenience with long relation names, INSERT
INTO now can alias its target table.

Bumps catversion as stored rules change.

Author: Peter Geoghegan, with significant contributions from Heikki
    Linnakangas and Andres Freund. Testing infrastructure by Jeff Janes.
Reviewed-By: Heikki Linnakangas, Andres Freund, Robert Haas, Simon Riggs,
    Dean Rasheed, Stephen Frost and many others.

1 files changed, 59 insertions, 7 deletions

diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index 88424964ef3..ea388182692 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -64,6 +64,8 @@ static void DecodeInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 static void DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 static void DecodeDelete(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 static void DecodeMultiInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeSpecConfirm(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+
 static void DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 						 xl_xact_parsed_commit *parsed, TransactionId xid);
 static void DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
@@ -414,6 +416,11 @@ DecodeHeapOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 			ReorderBufferXidSetCatalogChanges(ctx->reorder, xid, buf->origptr);
 			break;
 
+		case XLOG_HEAP_CONFIRM:
+			if (SnapBuildProcessChange(builder, xid, buf->origptr))
+				DecodeSpecConfirm(ctx, buf);
+			break;
+
 		case XLOG_HEAP_LOCK:
 			/* we don't care about row level locks for now */
 			break;
@@ -564,11 +571,15 @@ DecodeInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 		return;
 
 	change = ReorderBufferGetChange(ctx->reorder);
-	change->action = REORDER_BUFFER_CHANGE_INSERT;
+	if (!(xlrec->flags & XLH_INSERT_IS_SPECULATIVE))
+		change->action = REORDER_BUFFER_CHANGE_INSERT;
+	else
+		change->action = REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT;
 	change->origin_id = XLogRecGetOrigin(r);
+
 	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
 
-	if (xlrec->flags & XLOG_HEAP_CONTAINS_NEW_TUPLE)
+	if (xlrec->flags & XLH_INSERT_CONTAINS_NEW_TUPLE)
 	{
 		Size		tuplelen;
 		char	   *tupledata = XLogRecGetBlockData(r, 0, &tuplelen);
@@ -615,7 +626,7 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	change->origin_id = XLogRecGetOrigin(r);
 	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
 
-	if (xlrec->flags & XLOG_HEAP_CONTAINS_NEW_TUPLE)
+	if (xlrec->flags & XLH_UPDATE_CONTAINS_NEW_TUPLE)
 	{
 		data = XLogRecGetBlockData(r, 0, &datalen);
 
@@ -624,7 +635,7 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 		DecodeXLogTuple(data, datalen, change->data.tp.newtuple);
 	}
 
-	if (xlrec->flags & XLOG_HEAP_CONTAINS_OLD)
+	if (xlrec->flags & XLH_UPDATE_CONTAINS_OLD)
 	{
 		/* caution, remaining data in record is not aligned */
 		data = XLogRecGetData(r) + SizeOfHeapUpdate;
@@ -660,6 +671,13 @@ DecodeDelete(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	if (target_node.dbNode != ctx->slot->data.database)
 		return;
 
+	/*
+	 * Super deletions are irrelevant for logical decoding, it's driven by the
+	 * confirmation records.
+	 */
+	if (xlrec->flags & XLH_DELETE_IS_SUPER)
+		return;
+
 	/* output plugin doesn't look for this origin, no need to queue */
 	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
 		return;
@@ -671,7 +689,7 @@ DecodeDelete(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
 
 	/* old primary key stored */
-	if (xlrec->flags & XLOG_HEAP_CONTAINS_OLD)
+	if (xlrec->flags & XLH_DELETE_CONTAINS_OLD)
 	{
 		Assert(XLogRecGetDataLen(r) > (SizeOfHeapDelete + SizeOfHeapHeader));
 
@@ -737,7 +755,7 @@ DecodeMultiInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 		 * We decode the tuple in pretty much the same way as DecodeXLogTuple,
 		 * but since the layout is slightly different, we can't use it here.
 		 */
-		if (xlrec->flags & XLOG_HEAP_CONTAINS_NEW_TUPLE)
+		if (xlrec->flags & XLH_INSERT_CONTAINS_NEW_TUPLE)
 		{
 			change->data.tp.newtuple = ReorderBufferGetTupleBuf(ctx->reorder);
 
@@ -775,7 +793,7 @@ DecodeMultiInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 		 * xl_multi_insert_tuple record emitted by one heap_multi_insert()
 		 * call.
 		 */
-		if (xlrec->flags & XLOG_HEAP_LAST_MULTI_INSERT &&
+		if (xlrec->flags & XLH_INSERT_LAST_IN_MULTI &&
 			(i + 1) == xlrec->ntuples)
 			change->data.tp.clear_toast_afterwards = true;
 		else
@@ -788,6 +806,40 @@ DecodeMultiInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 }
 
 /*
+ * Parse XLOG_HEAP_CONFIRM from wal into a confirmation change.
+ *
+ * This is pretty trivial, all the state essentially already setup by the
+ * speculative insertion.
+ */
+static void
+DecodeSpecConfirm(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	XLogReaderState *r = buf->record;
+	ReorderBufferChange *change;
+	RelFileNode target_node;
+
+	/* only interested in our database */
+	XLogRecGetBlockTag(r, 0, &target_node, NULL, NULL);
+	if (target_node.dbNode != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	change = ReorderBufferGetChange(ctx->reorder);
+	change->action = REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM;
+	change->origin_id = XLogRecGetOrigin(r);
+
+	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
+
+	change->data.tp.clear_toast_afterwards = true;
+
+	ReorderBufferQueueChange(ctx->reorder, XLogRecGetXid(r), buf->origptr, change);
+}
+
+
+/*
  * Read a HeapTuple as WAL logged by heap_insert, heap_update and heap_delete
  * (but not by heap_multi_insert) into a tuplebuf.
  *