Thread: pgsql: Avoid updating our PgBackendStatus entry when track_activities i

Avoid updating our PgBackendStatus entry when track_activities is off.

The point of turning off track_activities is to avoid this reporting
overhead, but a thinko in commit 4f42b546fd87a80be30c53a0f2c897acb826ad52
caused pgstat_report_activity() to perform half of its updates anyway.
Fix that, and also make sure that we clear all the now-disabled fields
when transitioning to the non-reporting state.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/f7b0006f42913b6d641c9f0bef6fad1f670b9194

Modified Files
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src/backend/postmaster/pgstat.c     |   42 +++++++++++++++++++---------------
src/backend/utils/adt/pgstatfuncs.c |   11 +-------
2 files changed, 25 insertions(+), 28 deletions(-)