vinyl: allocate upsert counter on lsregion

Currently, we store upsert counter in tuple metadata (that's what
upsert_format is for), but since it's only relevant for tuples of
the memory level, we can store it on lsregion, right before tuple
data. Let's do it now so that we can get rid of upsert_format.

src/box/vy_stmt.c

@@ -134,13 +134,26 @@ struct tuple *
 vy_stmt_dup_lsregion(const struct tuple *stmt, struct lsregion *lsregion,
 		     int64_t alloc_id)
 {
+	enum iproto_type type = vy_stmt_type(stmt);
 	size_t size = tuple_size(stmt);
+	size_t alloc_size = size;
 	struct tuple *mem_stmt;
-	mem_stmt = lsregion_alloc(lsregion, size, alloc_id);
+
+	/* Reserve one byte for UPSERT counter. */
+	if (type == IPROTO_UPSERT)
+		alloc_size++;
+
+	mem_stmt = lsregion_alloc(lsregion, alloc_size, alloc_id);
 	if (mem_stmt == NULL) {
 		diag_set(OutOfMemory, size, "lsregion_alloc", "mem_stmt");
 		return NULL;
 	}
+
+	if (type == IPROTO_UPSERT) {
+		*(uint8_t *)mem_stmt = 0;
+		mem_stmt = (struct tuple *)((uint8_t *)mem_stmt + 1);
+	}
+
 	memcpy(mem_stmt, stmt, size);
 	/*
 	 * Region allocated statements can't be referenced or unreferenced
@@ -269,13 +282,8 @@ vy_stmt_new_upsert(struct tuple_format *format, const char *tuple_begin,
 	 * memory.
 	 */
 	assert(format->extra_size == sizeof(uint8_t));
-	struct tuple *upsert =
-		vy_stmt_new_with_ops(format, tuple_begin, tuple_end,
-				     operations, ops_cnt, IPROTO_UPSERT);
-	if (upsert == NULL)
-		return NULL;
-	vy_stmt_set_n_upserts(upsert, 0);
-	return upsert;
+	return vy_stmt_new_with_ops(format, tuple_begin, tuple_end,
+				    operations, ops_cnt, IPROTO_UPSERT);
 }
 
 struct tuple *

src/box/vy_stmt.h

@@ -146,23 +146,28 @@ vy_stmt_set_type(struct tuple *stmt, enum iproto_type type)
 	((struct vy_stmt *) stmt)->type = type;
 }
 
-/** Get upserts count of the vinyl statement. */
+/**
+ * Get upserts count of the vinyl statement.
+ * Only for UPSERT statements allocated on lsregion.
+ */
 static inline uint8_t
 vy_stmt_n_upserts(const struct tuple *stmt)
 {
-	assert(tuple_format(stmt)->extra_size == sizeof(uint8_t));
-	return *((const uint8_t *) tuple_extra(stmt));
+	assert(stmt->refs == 0);
+	assert(vy_stmt_type(stmt) == IPROTO_UPSERT);
+	return *((uint8_t *)stmt - 1);
 }
 
-/** Set upserts count of the vinyl statement. */
+/**
+ * Set upserts count of the vinyl statement.
+ * Only for UPSERT statements allocated on lsregion.
+ */
 static inline void
 vy_stmt_set_n_upserts(struct tuple *stmt, uint8_t n)
 {
-	struct tuple_format *format = tuple_format(stmt);
-	assert(format->extra_size == sizeof(uint8_t));
-	char *extra = (char *) stmt + stmt->data_offset -
-		      tuple_format_meta_size(format);
-	*((uint8_t *) extra) = n;
+	assert(stmt->refs == 0);
+	assert(vy_stmt_type(stmt) == IPROTO_UPSERT);
+	*((uint8_t *)stmt - 1) = n;
 }
 
 /** Get the column mask of the specified tuple. */