Commit 68075175 authored by unknown's avatar unknown
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ha_innodb.cc: 

  "Add a comment why data modifying SQL statements MUST always use a locking read in tables that they read: otherwise the execution is not serializable, and in many cases is not well-defined; we also merged the associated bug fix from 4.1"


sql/ha_innodb.cc:
  Add a comment why data modifying SQL statements MUST always use a locking read in tables that they read: otherwise the exxecution is not serializable, and in many cases is not well-defined; 5 minutes ago we merged the associated bug fix from 4.0 and 4.1
parent b69ea6d1

sql/ha_innodb.cc

+6 −1
Original line number Diff line number Diff line
@@ -5717,7 +5717,12 @@ ha_innobase::store_lock( 
		MySQL is doing LOCK TABLES ... READ.

		5) we let InnoDB do locking reads for all SQL statements that

		are not simple SELECTs; note that select_lock_type in this

		case may get strengthened in ::external_lock() to LOCK_X. */

		case may get strengthened in ::external_lock() to LOCK_X.

		Note that we MUST use a locking read in all data modifying

		SQL statements, because otherwise the execution would not be

		serializable, and also the results from the update could be

		unexpected if an obsolete consistent read view would be

		used. */



		prebuilt->select_lock_type = LOCK_S;

		prebuilt->stored_select_lock_type = LOCK_S;