sections now isn't nested. All user-defined functions now is
called outside critsections. Small improvements in WAL
protocol.
TODO: improve XLOG replay
This formulation requires every AM to provide amvacuumcleanup, unlike before,
but it's surely a whole lot cleaner. Also, add an 'amstorage' column to
pg_am so that we can get rid of hardwired knowledge in DefineOpClass().
misleadingly-named WriteBuffer routine, and instead require routines that
change buffer pages to call MarkBufferDirty (which does exactly what it says).
We also require that they do so before calling XLogInsert; this takes care of
the synchronization requirement documented in SyncOneBuffer. Note that
because bufmgr takes the buffer content lock (in shared mode) while writing
out any buffer, it doesn't matter whether MarkBufferDirty is executed before
the buffer content change is complete, so long as the content change is
completed before releasing exclusive lock on the buffer. So it's OK to set
the dirtybit before we fill in the LSN.
This eliminates the former kluge of needing to set the dirtybit in LockBuffer.
Aside from making the code more transparent, we can also add some new
debugging assertions, in particular that the caller of MarkBufferDirty must
hold the buffer content lock, not merely a pin.
torn-page problems. This introduces some issues of its own, mainly
that there are now some critical sections of unreasonably broad scope,
but it's a step forward anyway. Further cleanup will require some
code refactoring that I'd prefer to get Oleg and Teodor involved in.
partial. None of the existing AMs do anything useful except counting
tuples when there's nothing to delete, and we can get a tuple count
from the heap as long as it's not a partial index. (hash actually can
skip anyway because it maintains a tuple count in the index metapage.)
GIST is not currently able to exploit this optimization because, due to
failure to index NULLs, GIST is always effectively partial. Possibly
we should fix that sometime.
Simon Riggs w/ some review by Tom Lane.
comment line where output as too long, and update typedefs for /lib
directory. Also fix case where identifiers were used as variable names
in the backend, but as typedefs in ecpg (favor the backend for
indenting).
Backpatch to 8.1.X.
on a page, as suggested by ITAGAKI Takahiro. Also, change a few places
that were using some other estimates of max-items-per-page to consistently
use MaxOffsetNumber. This is conservatively large --- we could have used
the new MaxHeapTuplesPerPage macro, or a similar one for index tuples ---
but those places are simply declaring a fixed-size buffer and assuming it
will work, rather than actively testing for overrun. It seems safer to
size these buffers in a way that can't overflow even if the page is
corrupt.
- full concurrency for insert/update/select/vacuum:
- select and vacuum never locks more than one page simultaneously
- select (gettuple) hasn't any lock across it's calls
- insert never locks more than two page simultaneously:
- during search of leaf to insert it locks only one page
simultaneously
- while walk upward to the root it locked only parent (may be
non-direct parent) and child. One of them X-lock, another may
be S- or X-lock
- 'vacuum full' locks index
- improve gistgetmulti
- simplify XLOG records
Fix bug in index_beginscan_internal: LockRelation may clean
rd_aminfo structure, so move GET_REL_PROCEDURE after LockRelation
2. improve vacuum for gist
- use FSM
- full vacuum:
- reforms parent tuple if it's needed
( tuples was deleted on child page or parent tuple remains invalid
after crash recovery )
- truncate index file if possible
3. fixes bugs and mistakes
Bruce Momjian