[JPA_SPEC-62] Standard name and value for "read-only" query hint Created: 22/Jun/13 Updated: 11/Dec/15
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Relational databases typically benefit from the knowledge, whether a transation will potentially modify and information (so locks are needed), or only read-only queries are executed (so no locks are needed). For similar reason, EclipseLink (and hopefully other JPA implementations, too) know query hints for "ready-only".
Unfortunately when using such vendor-specific hints, this will induce the problem that a portable application must know all these hints for all JPA implementations (or there will be no Performance gain for the unknown ones). This is not smart from the view of an ISV.
Hence I want to propose that the next maintenance release of the JPA specification defines a unique name and value to enable the read-only query mode independently of the actual JPA implementation.
Proposal: A compliant implementation which has a read-only query mode MUST enable this read-only query mode when the "javax.persistence.readonly" with a value of "true" is provided.
|Comment by mkarg [ 09/Dec/15 ]|
I would really appreciate it if someone of the JPA spec team could at least comment on this more than two years old proposal.
|Comment by Lukas Jungmann [ 11/Dec/15 ]|
this make sense to me. Should check if there are other useful/commonly used hints to be defined by the spec.
|Comment by pbenedict [ 11/Dec/15 ]|
For clarity's sake, EclipseLink's "read-only" hint regards how it manages the first-level cache during a query; it's not about a making the transaction read-only.
|Comment by mkarg [ 11/Dec/15 ]|
A general "read-only" JPA property should simply allow the application programmer to tell JPA that the result of the query will never get updated by the current transaction. Whetever conclusions a JPA implementation draws from this is completely up to the particular JPA implementation. If EclipseLink simply uses this internally for its own cache purposes, this is a valid use. Other implementations might additionally or instead use this flag to send a "FOR READ ONLY" hint to the JDBC driver so the database can relax locking, etc.