## E.7. Release 9.5.18

Release date: 2019-06-20

This release contains a variety of fixes from 9.5.17. For information about new features in the 9.5 major release, see Section E.25.

### E.7.1. Migration to Version 9.5.18

A dump/restore is not required for those running 9.5.X.

However, if you are upgrading from a version earlier than 9.5.13, see Section E.12.

### E.7.2. Changes

- Fix failure of `ALTER TABLE ... ALTER COLUMN TYPE` when the table has a partial exclusion constraint (Tom Lane)

- Fix failure of `COMMENT` command for comments on domain constraints (Daniel Gustafsson, Michael Paquier)

- Fix incorrect printing of queries with duplicate join names (Philip Dubé)

  This oversight caused a dump/restore failure for views containing such queries.

- Fix misoptimization of `{1,1}` quantifiers in regular expressions (Tom Lane)

  Such quantifiers were treated as no-ops and optimized away; but the documentation specifies that they impose greediness, or non-greediness in the case of the non-greedy variant `{1,1}?`, on the subexpression they're attached to, and this did not happen. The misbehavior occurred only if the subexpression contained capturing parentheses or a back-reference.

- Avoid possible failures while initializing a new process's `pg_stat_activity` data (Tom Lane)

  Certain operations that could fail, such as converting strings extracted from an SSL certificate into the database encoding, were being performed inside a critical section. Failure there would result in database-wide lockup due to violating the access protocol for shared `pg_stat_activity` data.

- Fix race condition in check to see whether a pre-existing shared memory segment is still in use by a conflicting postmaster (Tom Lane)

- Avoid attempting to do database accesses for parameter checking in processes that are not connected to a specific database (Vignesh C, Andres Freund)

  This error could result in failures like “cannot read pg_class without having selected a database”.

- Avoid possible hang in libpq if using SSL and OpenSSL's pending-data buffer contains an exact multiple of 256 bytes (David Binderman)

- Improve initdb's handling of multiple equivalent names for the system time zone (Tom Lane, Andrew Gierth)

  Make initdb examine the `/etc/localtime` symbolic link, if that exists, to break ties between equivalent names for the system time zone. This makes initdb more likely to select the time zone name that the user would expect when multiple identical time zones exist. It will not change the behavior if `/etc/localtime` is not a symlink to a zone data file, nor if the time zone is determined from the `TZ` environment variable.

  Separately, prefer `UTC` over other spellings of that time zone, when neither `TZ` nor `/etc/localtime` provide a hint. This fixes an annoyance introduced by tzdata 2019a's change to make the `UCT` and `UTC` zone names equivalent: initdb was then preferring `UCT`, which almost nobody wants.

- Fix misleading error reports from reindexdb (Julien Rouhaud)

- Ensure that vacuumdb returns correct status if an error occurs while using parallel jobs (Julien Rouhaud)

- In `contrib/postgres_fdw`, account for possible data modifications by local `BEFORE ROW UPDATE` triggers (Shohei Mochizuki)

  If a trigger modified a column that was otherwise not changed by the `UPDATE`, the new value was not transmitted to the remote server.

- On Windows, avoid failure when the database encoding is set to SQL_ASCII and we attempt to log a non-ASCII string (Noah Misch)

  The code had been assuming that such strings must be in UTF-8, and would throw an error if they didn't appear to be validly encoded. Now, just transmit the untranslated bytes to the log.

- Make PL/pgSQL's header files C++-safe (George Tarasov)