Re: [Tarantool-patches] [PATCH 2/2] vinyl: clean-up read views if *_build_history() fails

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

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Thanks for the patch!

See 2 comments below.

> diff --git a/src/box/vy_write_iterator.c b/src/box/vy_write_iterator.c
> index 7a6a20627..f6e6ed4d2 100644
> --- a/src/box/vy_write_iterator.c
> +++ b/src/box/vy_write_iterator.c
> @@ -961,8 +961,11 @@ vy_write_iterator_build_read_views(struct vy_write_iterator *stream, int *count)
>  	size_t used = region_used(region);
>  	stream->rv_used_count = 0;
>  	if (vy_write_iterator_build_history(stream, &raw_count,
> -					    &is_first_insert) != 0)
> +					    &is_first_insert) != 0) {
> +		for (int i = 0; i < stream->rv_count; ++i)
> +			stream->read_views[i].history = NULL;
>  		goto error;

1. Kostja probably meant encapsulation of function
vy_write_iterator_build_history(). Currently that function
leaves garbage in case of a fail. Therefore it becomes not
self sufficient. Better cleanup the views in the same place
where they are created - inside build_history().

Imagine, if build_history() would be called not in a single
place. We would need to cleanup its garbage in each one.

Diff below and attached as a file.
====================
diff --git a/src/box/vy_write_iterator.c b/src/box/vy_write_iterator.c
index f6e6ed4d2..7d8c60d73 100644
--- a/src/box/vy_write_iterator.c
+++ b/src/box/vy_write_iterator.c
@@ -790,8 +790,11 @@ next_lsn:
 	 * statement around if this is major compaction, because
 	 * there's no tuple it could overwrite.
 	 */
-	if (rc == 0 && stream->is_last_level &&
-	    stream->deferred_delete_stmt != NULL) {
+	if (rc != 0) {
+		for (int i = 0; i < stream->rv_count; ++i)
+			stream->read_views[i].history = NULL;
+	} else if (stream->is_last_level &&
+		   stream->deferred_delete_stmt != NULL) {
 		vy_stmt_unref_if_possible(stream->deferred_delete_stmt);
 		stream->deferred_delete_stmt = NULL;
 	}
@@ -961,11 +964,8 @@ vy_write_iterator_build_read_views(struct vy_write_iterator *stream, int *count)
 	size_t used = region_used(region);
 	stream->rv_used_count = 0;
 	if (vy_write_iterator_build_history(stream, &raw_count,
-					    &is_first_insert) != 0) {
-		for (int i = 0; i < stream->rv_count; ++i)
-			stream->read_views[i].history = NULL;
+					    &is_first_insert) != 0)
 		goto error;
-	}
 	if (raw_count == 0) {
 		/* A key is fully optimized. */
 		region_truncate(region, used);
====================

2. I rolled back the patch and run the test - it passed. What can be a reason?

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diff --git a/src/box/vy_write_iterator.c b/src/box/vy_write_iterator.c
index f6e6ed4d2..7d8c60d73 100644
--- a/src/box/vy_write_iterator.c
+++ b/src/box/vy_write_iterator.c
@@ -790,8 +790,11 @@ next_lsn:
 	 * statement around if this is major compaction, because
 	 * there's no tuple it could overwrite.
 	 */
-	if (rc == 0 && stream->is_last_level &&
-	    stream->deferred_delete_stmt != NULL) {
+	if (rc != 0) {
+		for (int i = 0; i < stream->rv_count; ++i)
+			stream->read_views[i].history = NULL;
+	} else if (stream->is_last_level &&
+		   stream->deferred_delete_stmt != NULL) {
 		vy_stmt_unref_if_possible(stream->deferred_delete_stmt);
 		stream->deferred_delete_stmt = NULL;
 	}
@@ -961,11 +964,8 @@ vy_write_iterator_build_read_views(struct vy_write_iterator *stream, int *count)
 	size_t used = region_used(region);
 	stream->rv_used_count = 0;
 	if (vy_write_iterator_build_history(stream, &raw_count,
-					    &is_first_insert) != 0) {
-		for (int i = 0; i < stream->rv_count; ++i)
-			stream->read_views[i].history = NULL;
+					    &is_first_insert) != 0)
 		goto error;
-	}
 	if (raw_count == 0) {
 		/* A key is fully optimized. */
 		region_truncate(region, used);