Horton

Re: Parallel bitmap heap scan

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Jeff Janes <jeff.janes@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Thomas Munro <thomas.munro@enterprisedb.com>, Haribabu Kommi <kommi.haribabu@gmail.com>, Rafia Sabih <rafia.sabih@enterprisedb.com>, tushar <tushar.ahuja@enterprisedb.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-08T18:00:06Z
Lists: pgsql-hackers 
On Wed, Mar 8, 2017 at 12:53 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Thanks.  Sorry for the hassle; my compiler isn't as picky about this
>> as I would like, and apparently Dilip's isn't either.
>
> Might be interesting to see whether -O level affects it.  In principle,
> whether you get the warning should depend on how much the compiler has
> analyzed the logic flow ...

What I'm using is:

Configured with:
--prefix=/Applications/Xcode.app/Contents/Developer/usr
--with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin14.5.0
Thread model: posix

While I haven't experimented with this too extensively, my general
impression is that this thing is extremely tolerant of uninitialized
variables.  I just tried compiling nodeBitmapHeapscan.c with -Wall
-Werror and each of -O0, -O1, -O2, and -O3, and none of those produced
any warnings.  I've been reluctant to go to the hassle of installing a
different compiler...

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Pass DSA_ALLOC_HUGE when allocating a shared TIDBitmap.

  2. Support parallel bitmap heap scans.

  3. tidbitmap: Support shared iteration.

  4. Shut down Gather's children before shutting down Gather itself.

  5. Revise the way the element allocator for a simplehash is specified.

  6. Refactor bitmap heap scan estimation of heap pages fetched.

  7. Use more efficient hashtable for tidbitmap.c to speed up bitmap scans.