PostgreSQL 9.6.6 Documentation
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# E.125. Release 9.0.4

Release date: 2011-04-18

This release contains a variety of fixes from 9.0.3. For information about new features in the 9.0 major release, see Section E.129.

## E.125.1. Migration to Version 9.0.4

A dump/restore is not required for those running 9.0.X.

However, if your installation was upgraded from a previous major release by running pg_upgrade, you should take action to prevent possible data loss due to a now-fixed bug in pg_upgrade. The recommended solution is to run `VACUUM FREEZE` on all TOAST tables. More information is available at http://wiki.postgresql.org/wiki/20110408pg_upgrade_fix.

## E.125.2. Changes

- Fix pg_upgrade's handling of TOAST tables (Bruce Momjian)

  The `pg_class`.`relfrozenxid` value for TOAST tables was not correctly copied into the new installation during pg_upgrade. This could later result in `pg_clog` files being discarded while they were still needed to validate tuples in the TOAST tables, leading to "could not access status of transaction" failures.

  This error poses a significant risk of data loss for installations that have been upgraded with pg_upgrade. This patch corrects the problem for future uses of pg_upgrade, but does not in itself cure the issue in installations that have been processed with a buggy version of pg_upgrade.

- Suppress incorrect "PD_ALL_VISIBLE flag was incorrectly set" warning (Heikki Linnakangas)

  `VACUUM` would sometimes issue this warning in cases that are actually valid.

- Use better SQLSTATE error codes for hot standby conflict cases (Tatsuo Ishii and Simon Riggs)

  All retryable conflict errors now have an error code that indicates that a retry is possible. Also, session closure due to the database being dropped on the master is now reported as `ERRCODE_DATABASE_DROPPED`, rather than `ERRCODE_ADMIN_SHUTDOWN`, so that connection poolers can handle the situation correctly.

- Prevent intermittent hang in interactions of startup process with bgwriter process (Simon Riggs)

  This affected recovery in non-hot-standby cases.

- Disallow including a composite type in itself (Tom Lane)

  This prevents scenarios wherein the server could recurse infinitely while processing the composite type. While there are some possible uses for such a structure, they don't seem compelling enough to justify the effort required to make sure it always works safely.

- Avoid potential deadlock during catalog cache initialization (Nikhil Sontakke)

  In some cases the cache loading code would acquire share lock on a system index before locking the index's catalog. This could deadlock against processes trying to acquire exclusive locks in the other, more standard order.

- Fix dangling-pointer problem in `BEFORE ROW UPDATE` trigger handling when there was a concurrent update to the target tuple (Tom Lane)

  This bug has been observed to result in intermittent "cannot extract system attribute from virtual tuple" failures while trying to do `UPDATE RETURNING ctid`. There is a very small probability of more serious errors, such as generating incorrect index entries for the updated tuple.

- Disallow `DROP TABLE` when there are pending deferred trigger events for the table (Tom Lane)

  Formerly the `DROP` would go through, leading to "could not open relation with OID nnn" errors when the triggers were eventually fired.

- Allow "replication" as a user name in `pg_hba.conf` (Andrew Dunstan)

  "replication" is special in the database name column, but it was mistakenly also treated as special in the user name column.

- Prevent crash triggered by constant-false WHERE conditions during GEQO optimization (Tom Lane)

- Improve planner's handling of semi-join and anti-join cases (Tom Lane)

- Fix handling of `SELECT FOR UPDATE` in a sub-SELECT (Tom Lane)

  This bug typically led to "cannot extract system attribute from virtual tuple" errors.

- Fix selectivity estimation for text search to account for NULLs (Jesper Krogh)

- Fix get_actual_variable_range() to support hypothetical indexes injected by an index adviser plugin (Gurjeet Singh)

- Fix PL/Python memory leak involving array slices (Daniel Popowich)

- Allow libpq's SSL initialization to succeed when user's home directory is unavailable (Tom Lane)

  If the SSL mode is such that a root certificate file is not required, there is no need to fail. This change restores the behavior to what it was in pre-9.0 releases.

- Fix libpq to return a useful error message for errors detected in `conninfo_array_parse` (Joseph Adams)

  A typo caused the library to return NULL, rather than the `PGconn` structure containing the error message, to the application.

- Fix ecpg preprocessor's handling of float constants (Heikki Linnakangas)

- Fix parallel pg_restore to handle comments on POST_DATA items correctly (Arnd Hannemann)

- Fix pg_restore to cope with long lines (over 1KB) in TOC files (Tom Lane)

- Put in more safeguards against crashing due to division-by-zero with overly enthusiastic compiler optimization (Aurelien Jarno)

- Support use of dlopen() in FreeBSD and OpenBSD on MIPS (Tom Lane)

  There was a hard-wired assumption that this system function was not available on MIPS hardware on these systems. Use a compile-time test instead, since more recent versions have it.

- Fix compilation failures on HP-UX (Heikki Linnakangas)

- Avoid crash when trying to write to the Windows console very early in process startup (Rushabh Lathia)

- Support building with MinGW 64 bit compiler for Windows (Andrew Dunstan)

- Fix version-incompatibility problem with libintl on Windows (Hiroshi Inoue)

- Fix usage of xcopy in Windows build scripts to work correctly under Windows 7 (Andrew Dunstan)

  This affects the build scripts only, not installation or usage.

- Fix path separator used by pg_regress on Cygwin (Andrew Dunstan)

- Update time zone data files to tzdata release 2011f for DST law changes in Chile, Cuba, Falkland Islands, Morocco, Samoa, and Turkey; also historical corrections for South Australia, Alaska, and Hawaii.

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