From 3467bf485972065f73c25a8f1e66c7c4f0bd5d23 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sat, 25 Jan 2020 21:47:05 -0600
Subject: [PATCH v3 3/4] vacuum verbose: prefix write multi-line output to
 client..

..but do not change output to logfile, which isn't unclear.

I borrowed the format from ShowUsage.

TODO: lazy_cleanup_index
---
 src/backend/access/heap/vacuumlazy.c | 58 ++++++++++++++++++++++++++----------
 1 file changed, 43 insertions(+), 15 deletions(-)

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index eb903d5..6f85af7 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -307,6 +307,7 @@ static BufferAccessStrategy vac_strategy;
 static void lazy_scan_heap(Relation onerel, VacuumParams *params,
 						   LVRelStats *vacrelstats, Relation *Irel, int nindexes,
 						   bool aggressive);
+static void vacuum_msg(StringInfoData *buf, const char *prefix, LVRelStats *vacrelstats, double nkeep, double nunused, BlockNumber empty_pages, PGRUsage *ru0);
 static void lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats);
 static bool lazy_check_needs_freeze(Buffer buf, bool *hastup);
 static void lazy_vacuum_all_indexes(Relation onerel, Relation *Irel,
@@ -717,7 +718,8 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 	BlockNumber next_unskippable_block;
 	bool		skipping_blocks;
 	xl_heap_freeze_tuple *frozen;
-	StringInfoData buf;
+	StringInfoData logdetail,
+				clientdetail;
 	const int	initprog_index[] = {
 		PROGRESS_VACUUM_PHASE,
 		PROGRESS_VACUUM_TOTAL_HEAP_BLKS,
@@ -1668,40 +1670,66 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 						RelationGetRelationName(onerel),
 						tups_vacuumed, vacuumed_pages)));
 
+	/* Write separate log messages to client (with prefix) and logfile (without prefix) */
+	vacuum_msg(&logdetail, "", vacrelstats, nkeep, nunused, empty_pages, &ru0);
+	vacuum_msg(&clientdetail, "! ", vacrelstats, nkeep, nunused, empty_pages, &ru0);
+
+	ereport(elevel,
+			(errmsg("\"%s\": found %.0f removable, %.0f nonremovable row versions in %u out of %u pages",
+					RelationGetRelationName(onerel),
+					tups_vacuumed, num_tuples,
+					vacrelstats->scanned_pages, nblocks),
+			 errdetail_log("%s", logdetail.data),
+			 errdetail_internal("%s", clientdetail.data)));
+
+	pfree(logdetail.data);
+	pfree(clientdetail.data);
+}
+
+/* Populate buf with string to be freed by caller */
+static void
+vacuum_msg(StringInfoData *buf, const char *prefix, LVRelStats *vacrelstats, double nkeep, double nunused, BlockNumber empty_pages, PGRUsage *ru0)
+{
 	/*
 	 * This is pretty messy, but we split it up so that we can skip emitting
 	 * individual parts of the message when not applicable.
 	 */
-	initStringInfo(&buf);
-	appendStringInfo(&buf, ngettext("%.0f dead row version cannot be removed yet, oldest xmin: %u\n",
+	initStringInfo(buf);
+	if (prefix)
+		appendStringInfoString(buf, prefix);
+	appendStringInfo(buf, ngettext("%.0f dead row version cannot be removed yet, oldest xmin: %u\n",
 									"%.0f dead row versions cannot be removed yet, oldest xmin: %u\n",
 									nkeep),
 					 nkeep, OldestXmin);
-	appendStringInfo(&buf, ngettext("There was %.0f unused item identifier.\n",
+
+	if (prefix)
+		appendStringInfoString(buf, prefix);
+	appendStringInfo(buf, ngettext("There was %.0f unused item identifier.\n",
 									"There were %.0f unused item identifiers.\n",
 									nunused),
 					 nunused);
-	appendStringInfo(&buf, ngettext("Skipped %u page due to buffer pins, ",
+
+	if (prefix)
+		appendStringInfoString(buf, prefix);
+	appendStringInfo(buf, ngettext("Skipped %u page due to buffer pins, ",
 									"Skipped %u pages due to buffer pins, ",
 									vacrelstats->pinskipped_pages),
 					 vacrelstats->pinskipped_pages);
-	appendStringInfo(&buf, ngettext("%u frozen page.\n",
+	appendStringInfo(buf, ngettext("%u frozen page.\n",
 									"%u frozen pages.\n",
 									vacrelstats->frozenskipped_pages),
 					 vacrelstats->frozenskipped_pages);
-	appendStringInfo(&buf, ngettext("%u page is entirely empty.\n",
+
+	if (prefix)
+		appendStringInfoString(buf, prefix);
+	appendStringInfo(buf, ngettext("%u page is entirely empty.\n",
 									"%u pages are entirely empty.\n",
 									empty_pages),
 					 empty_pages);
-	appendStringInfo(&buf, "%s.", pg_rusage_show(&ru0));
 
-	ereport(elevel,
-			(errmsg("\"%s\": found %.0f removable, %.0f nonremovable row versions in %u out of %u pages",
-					RelationGetRelationName(onerel),
-					tups_vacuumed, num_tuples,
-					vacrelstats->scanned_pages, nblocks),
-			 errdetail_internal("%s", buf.data)));
-	pfree(buf.data);
+	if (prefix)
+		appendStringInfoString(buf, prefix);
+	appendStringInfo(buf, "%s.", pg_rusage_show(ru0));
 }
 
 /*
-- 
2.7.4