Follow-up for the fix for bug #46947 "Embedded SELECT without
FOR UPDATE is causing a lock". This patch tries to address problems which were exposed during backporting of original patch to 5.1 tree. - It ensures that we don't change locking behavior of simple SELECT statements on InnoDB tables when they are executed under LOCK TABLES ... READ and with @@innodb_table_locks=0. Also we no longer pass TL_READ_DEFAULT/TL_WRITE_DEFAULT lock types, which are supposed to be parser-only, to handler::start_stmt() method. - It makes check_/no_concurrent_insert.inc auxiliary scripts more robust against changes in test cases that use them and also ensures that they don't unnecessarily change environment of caller. mysql-test/include/check_concurrent_insert.inc: Reset DEBUG_SYNC facility before and after using it in auxiliary script. This makes this script more robust against changes in test cases calling it. It also ensures that script does not unnecessarily change environment of caller. mysql-test/include/check_no_concurrent_insert.inc: Reset DEBUG_SYNC facility before and after using it in auxiliary script. This makes this script more robust against changes in test cases calling it. It also ensures that script does not unnecessarily change environment of caller. mysql-test/r/innodb-lock.result: Added coverage for LOCK TABLES ... READ behavior in @@innodb_table_locks = 0 mode. This test also checks that an appropriate type of lock is passed to handler::start_stmt() method. mysql-test/t/innodb-lock.test: Added coverage for LOCK TABLES ... READ behavior in @@innodb_table_locks = 0 mode. This test also checks that an appropriate type of lock is passed to handler::start_stmt() method. sql/sql_base.cc: Since we no longer set TL_READ as lock type for tables used in simple SELECT right in the parser, in order to preserve behavior for such statements on InnoDB tables when in LOCK TABLES mode with @innodb_table_locks = 0, check_lock_and_start_stmt() had to be changed to convert TL_READ_DEFAULT to an appropriate type of read lock before passing it to handler::start_stmt() method. We do similar thing for TL_WRITE_DEFAULT as this lock type is also supposed to be parser-only type. As consequence read_lock_type_for_table() had to be adjusted to behave properly when it is called from check_lock_and_start_stmt() in prelocked mode.
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