On Monday, June 9, 2014, Ian Barwick <
ian@2ndquadrant.com> wrote:
On 09/06/14 14:47, David G Johnston wrote:
Ian Barwick wrote
Hi,
The JDBC API provides the getGeneratedKeys() method as a way of retrieving
primary key values without the need to explicitly specify the primary key
column(s). This is a widely-used feature, however the implementation has
significant
performance drawbacks.
Currently this feature is implemented in the JDBC driver by appending
"RETURNING *" to the supplied statement. However this means all columns of
affected rows will be returned to the client, which causes significant
performance problems, particularly on wide tables. To mitigate this, it
would
be desirable to enable the JDBC driver to request only the primary key
value(s).
ISTM that having a non-null returning clause variable when no returning is present in the command makes things more complicated and introduces unnecessary checks in the not uncommon case of multiple non-returning commands being issued in series.
returningList was able to be null and so should returningClause. Then if non-null first check for the easy column listing and then check for the more expensive PK lookup request.
Then again the extra returning checks may just amount noise.
