Revert recovery prefetching feature.

This set of commits has some bugs with known fixes, but at this late
stage in the release cycle it seems best to revert and resubmit next
time, along with some new automated test coverage for this whole area.

Commits reverted:

dc88460c: Doc: Review for "Optionally prefetch referenced data in recovery."
1d257577: Optionally prefetch referenced data in recovery.
f003d9f8: Add circular WAL decoding buffer.
323cbe7c: Remove read_page callback from XLogReader.

Remove the new GUC group WAL_RECOVERY recently added by a55a9847, as the
corresponding section of config.sgml is now reverted.

Discussion: https://postgr.es/m/CAOuzzgrn7iKnFRsB4MHp3UisEQAGgZMbk_ViTN4HV4-Ksq8zCg%40mail.gmail.com

1 files changed, 8 insertions, 18 deletions

diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 00543ede45a..ffc6160e9f3 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -148,8 +148,7 @@ StartupDecodingContext(List *output_plugin_options,
 					   TransactionId xmin_horizon,
 					   bool need_full_snapshot,
 					   bool fast_forward,
-					   LogicalDecodingXLogPageReadCB page_read,
-					   WALSegmentCleanupCB cleanup_cb,
+					   XLogReaderRoutine *xl_routine,
 					   LogicalOutputPluginWriterPrepareWrite prepare_write,
 					   LogicalOutputPluginWriterWrite do_write,
 					   LogicalOutputPluginWriterUpdateProgress update_progress)
@@ -199,12 +198,11 @@ StartupDecodingContext(List *output_plugin_options,
 
 	ctx->slot = slot;
 
-	ctx->reader = XLogReaderAllocate(wal_segment_size, NULL, cleanup_cb);
+	ctx->reader = XLogReaderAllocate(wal_segment_size, NULL, xl_routine, ctx);
 	if (!ctx->reader)
 		ereport(ERROR,
 				(errcode(ERRCODE_OUT_OF_MEMORY),
 				 errmsg("out of memory")));
-	ctx->page_read = page_read;
 
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
@@ -321,8 +319,7 @@ CreateInitDecodingContext(const char *plugin,
 						  List *output_plugin_options,
 						  bool need_full_snapshot,
 						  XLogRecPtr restart_lsn,
-						  LogicalDecodingXLogPageReadCB page_read,
-						  WALSegmentCleanupCB cleanup_cb,
+						  XLogReaderRoutine *xl_routine,
 						  LogicalOutputPluginWriterPrepareWrite prepare_write,
 						  LogicalOutputPluginWriterWrite do_write,
 						  LogicalOutputPluginWriterUpdateProgress update_progress)
@@ -425,7 +422,7 @@ CreateInitDecodingContext(const char *plugin,
 
 	ctx = StartupDecodingContext(NIL, restart_lsn, xmin_horizon,
 								 need_full_snapshot, false,
-								 page_read, cleanup_cb, prepare_write, do_write,
+								 xl_routine, prepare_write, do_write,
 								 update_progress);
 
 	/* call output plugin initialization callback */
@@ -479,8 +476,7 @@ LogicalDecodingContext *
 CreateDecodingContext(XLogRecPtr start_lsn,
 					  List *output_plugin_options,
 					  bool fast_forward,
-					  LogicalDecodingXLogPageReadCB page_read,
-					  WALSegmentCleanupCB cleanup_cb,
+					  XLogReaderRoutine *xl_routine,
 					  LogicalOutputPluginWriterPrepareWrite prepare_write,
 					  LogicalOutputPluginWriterWrite do_write,
 					  LogicalOutputPluginWriterUpdateProgress update_progress)
@@ -532,8 +528,8 @@ CreateDecodingContext(XLogRecPtr start_lsn,
 
 	ctx = StartupDecodingContext(output_plugin_options,
 								 start_lsn, InvalidTransactionId, false,
-								 fast_forward, page_read, cleanup_cb,
-								 prepare_write, do_write, update_progress);
+								 fast_forward, xl_routine, prepare_write,
+								 do_write, update_progress);
 
 	/* call output plugin initialization callback */
 	old_context = MemoryContextSwitchTo(ctx->context);
@@ -589,13 +585,7 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 		char	   *err = NULL;
 
 		/* the read_page callback waits for new WAL */
-		while (XLogReadRecord(ctx->reader, &record, &err) ==
-			   XLREAD_NEED_DATA)
-		{
-			if (!ctx->page_read(ctx->reader))
-				break;
-		}
-
+		record = XLogReadRecord(ctx->reader, &err);
 		if (err)
 			elog(ERROR, "%s", err);
 		if (!record)