PostgreSQL 9.2.4 Documentation
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# E.41. Release 8.4.6

> Release Date: 2010-12-16

This release contains a variety of fixes from 8.4.5. For information about new features in the 8.4 major release, see Section E.47.

## E.41.1. Migration to Version 8.4.6

A dump/restore is not required for those running 8.4.X. However, if you are upgrading from a version earlier than 8.4.2, see the release notes for 8.4.2.

## E.41.2. Changes

- Force the default `wal_sync_method` to be `fdatasync` on Linux (Tom Lane, Marti Raudsepp)

  The default on Linux has actually been `fdatasync` for many years, but recent kernel changes caused PostgreSQL to choose `open_datasync` instead. This choice did not result in any performance improvement, and caused outright failures on certain filesystems, notably `ext4` with the `data=journal` mount option.

- Fix assorted bugs in WAL replay logic for GIN indexes (Tom Lane)

  This could result in "bad buffer id: 0" failures or corruption of index contents during replication.

- Fix recovery from base backup when the starting checkpoint WAL record is not in the same WAL segment as its redo point (Jeff Davis)

- Fix persistent slowdown of autovacuum workers when multiple workers remain active for a long time (Tom Lane)

  The effective `vacuum_cost_limit` for an autovacuum worker could drop to nearly zero if it processed enough tables, causing it to run extremely slowly.

- Add support for detecting register-stack overrun on `IA64` (Tom Lane)

  The `IA64` architecture has two hardware stacks. Full prevention of stack-overrun failures requires checking both.

- Add a check for stack overflow in `copyObject()` (Tom Lane)

  Certain code paths could crash due to stack overflow given a sufficiently complex query.

- Fix detection of page splits in temporary GiST indexes (Heikki Linnakangas)

  It is possible to have a "concurrent" page split in a temporary index, if for example there is an open cursor scanning the index when an insertion is done. GiST failed to detect this case and hence could deliver wrong results when execution of the cursor continued.

- Fix error checking during early connection processing (Tom Lane)

  The check for too many child processes was skipped in some cases, possibly leading to postmaster crash when attempting to add the new child process to fixed-size arrays.

- Improve efficiency of window functions (Tom Lane)

  Certain cases where a large number of tuples needed to be read in advance, but `work_mem` was large enough to allow them all to be held in memory, were unexpectedly slow. `percent_rank()`, `cume_dist()` and `ntile()` in particular were subject to this problem.

- Avoid memory leakage while `ANALYZE`'ing complex index expressions (Tom Lane)

- Ensure an index that uses a whole-row Var still depends on its table (Tom Lane)

  An index declared like `create index i on t (foo(t.*))` would not automatically get dropped when its table was dropped.

- Do not "inline" a SQL function with multiple `OUT` parameters (Tom Lane)

  This avoids a possible crash due to loss of information about the expected result rowtype.

- Behave correctly if `ORDER BY`, `LIMIT`, `FOR UPDATE`, or `WITH` is attached to the `VALUES` part of `INSERT ... VALUES` (Tom Lane)

- Fix constant-folding of `COALESCE()` expressions (Tom Lane)

  The planner would sometimes attempt to evaluate sub-expressions that in fact could never be reached, possibly leading to unexpected errors.

- Fix postmaster crash when connection acceptance (`accept()` or one of the calls made immediately after it) fails, and the postmaster was compiled with GSSAPI support (Alexander Chernikov)

- Fix missed unlink of temporary files when `log_temp_files` is active (Tom Lane)

  If an error occurred while attempting to emit the log message, the unlink was not done, resulting in accumulation of temp files.

- Add print functionality for `InhRelation` nodes (Tom Lane)

  This avoids a failure when `debug_print_parse` is enabled and certain types of query are executed.

- Fix incorrect calculation of distance from a point to a horizontal line segment (Tom Lane)

  This bug affected several different geometric distance-measurement operators.

- Fix incorrect calculation of transaction status in ecpg (Itagaki Takahiro)

- Fix PL/pgSQL's handling of "simple" expressions to not fail in recursion or error-recovery cases (Tom Lane)

- Fix PL/Python's handling of set-returning functions (Jan Urbanski)

  Attempts to call SPI functions within the iterator generating a set result would fail.

- Fix bug in `contrib/cube`'s GiST picksplit algorithm (Alexander Korotkov)

  This could result in considerable inefficiency, though not actually incorrect answers, in a GiST index on a `cube` column. If you have such an index, consider `REINDEX`ing it after installing this update.

- Don't emit "identifier will be truncated" notices in `contrib/dblink` except when creating new connections (Itagaki Takahiro)

- Fix potential coredump on missing public key in `contrib/pgcrypto` (Marti Raudsepp)

- Fix memory leak in `contrib/xml2`'s XPath query functions (Tom Lane)

- Update time zone data files to tzdata release 2010o for DST law changes in Fiji and Samoa; also historical corrections for Hong Kong.

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