MySQL Bugs: #56488: NdbApi : Improve Blob/internal operation management

Bug #56488	NdbApi : Improve Blob/internal operation management
Submitted:	2 Sep 2010 9:46	Modified:	18 Dec 2016 20:32
Reporter:	Frazer Clement	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Cluster: NDB API	Severity:	S3 (Non-critical)
Version:	mysql-5.1-telco-6.2	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Accesses to Blob columns cause NdbApi to insert extra 'internal' operations into the user transaction's operation lists for retrieving/maintaining the Blob head and the Blob part table rows.

This can cause problems :
 1) When scanning a table with Blobs, each nextResult() call issues read operations for the Blob part table(s).  These operations are not automatically freed. (Bug # 52313)

 2) Implicit execute() calls can break expected Blob state transitions (bug#50310).  Where some user operations are defined which access Blobs, then a separate scan of a Blob containing table is advanced with nextResult(), the implicit execute() within the nextResult() can cause the Blob-accessing user operations to be executed without correct state transitions.

 3) When iterating through completed operations, internal operations which the user is conceptually unaware of, are visible.

How to repeat:
See above bug numbers.

Suggested fix:
Improve the encapsulation of the Blob internal operations :
 - Make the 'internal' nature of the Blob operations explicit.
 - Manage them separately from the user's operations.
 - Execute them only when expected.
 - Free them after they have been processed.