Improved code comment and removed nop test

sql/sql_join_cache.h

@@ -206,11 +206,14 @@ class JOIN_CACHE :public Sql_alloc
 
   /* 
     This flag indicates that records written into the join buffer contain
-    a match flag field. The flag must be set by the init method.
+    a match flag field.
+    This is set to true for the first inner table of an outer join or a
+    semi-join.
+    The flag must be set by the init method.
     Currently any implementation of the virtial init method calls
     the function JOIN_CACHE::calc_record_fields() to set this flag.
   */
-  bool with_match_flag; 
+  bool with_match_flag;
   /*
     This flag indicates that any record is prepended with the length of the
     record which allows us to skip the record or part of it without reading.

sql/sql_select.h

@@ -566,7 +566,7 @@ typedef struct st_join_table {
   }
   bool is_first_inner_for_outer_join()
   {
-    return first_inner && first_inner == this;
+    return first_inner == this;
   }
   bool use_match_flag()
   {

sql/sql_table.cc

@@ -6899,10 +6899,8 @@ static bool mysql_inplace_alter_table(THD *thd,
   Alter_info *alter_info= ha_alter_info->alter_info;
   bool reopen_tables= false;
   bool res;
-
   const enum_alter_inplace_result inplace_supported=
     ha_alter_info->inplace_supported;
-
   DBUG_ENTER("mysql_inplace_alter_table");
 
   /* Downgrade DDL lock while we are waiting for exclusive lock below */
@@ -7152,7 +7150,7 @@ static bool mysql_inplace_alter_table(THD *thd,
     DBUG_RETURN(true);
   }
 
-  // Rename altered table if requested.
+  // Rename altered table in case of ALTER TABLE ... RENAME
   if (alter_ctx->is_table_renamed())
   {
     DBUG_ASSERT(!tdc_share_is_cached(thd, alter_ctx->db.str,

storage/maria/ha_s3.cc

@@ -736,7 +736,15 @@ static int s3_hton_panic(handlerton *hton, ha_panic_function flag)
 
 
 /**
-  Check if a table is in S3 as part of discovery
+  Check if a table is in S3 as part of discovery. Returns TABLE_SHARE if found.
+
+  @param hton           S3 handlerton
+  @param thd            MariaDB thd
+  @param [out] share    If table exists, this is updated to contain the found
+                        TABLE_SHARE (based on the .frm in S3)
+
+  @return 0  Table exists
+  @return #  Error number
 */
 
 static int s3_discover_table(handlerton *hton, THD* thd, TABLE_SHARE *share)