Hello, Please find attached an updated WIP patch. I have incorporated almost all comments. This is to be applied over Robert's patches. I will post performance results later on.
1. shift (>>) and AND (&) operations: The assign hook of wal_segment_size sets the WalModMask and WalShiftBit. All the modulo and division operations using XLogSegSize has been replaced with these. However, there are many preprocessors which divide with XLogSegSize in xlog_internal.h. I have not changed these because it would mean I will have to reassign the WalShiftBit along with XLogSegSize in all the modules which use these macros. That does not seem to be a good idea. Also, this means shift operator can be used only in couple of places. 2. pg_standby: it deals with WAL files, so I have used the file size to set the XLogSegSize (similar to pg_xlogdump). Also, macro MaxSegmentsPerLogFile using XLOG_SEG_SIZE is now defined in SetWALFileNameForCleanup where it is used. Since XLOG_SEG_SIZE is not preset, the code which throws an message if the file size is greater than XLOG_SEG_SIZE had to be removed. 3. XLOGChooseNumBuffers: This function, called during the creation of Shared Memory Segment, requires XLogSegSize which is set from the ControlFile. Hence temporarily read the ControlFile in XLOGShmemSize before invoking XLOGChooseNumBuffer. The ControlFile is read again and stored on the Shared Memory later on. 4. IsValidXLogSegSize: This is a macro to verify the XLogSegSize. This is used in initdb, pg_xlogdump, pg_standby. 5. Macro for power2: There were couple of ideas to make it centralised. For now, I have just defined it in xlog_internal. 6. Since CRC is used to verify the ControlFile before reading all the contents from it as is and I do not see the need to re-verify the xlog_seg_size. 7. min/max_wal_size still take values in KB unit and internally store it as segment count. Though the calculation is now shifted to their respective assign hook as the GUC_UNIT_XSEGS had to be removed. 8. Declaring XLogSegSize: There are 2 internal variables for the same parameter. In original code XLOG_SEG_SIZE is defined in the auto-generated file src/include/pg_config.h. And xlog_internal.h defines: #define XLogSegSize ((uint32) XLOG_SEG_SIZE) To avoid renaming all parts of code, I made the following change in xlog_internal.h + extern uint32 XLogSegSize; +#define XLOG_SEG_SIZE XLogSegSize would it be better to just use one variable XLogSegSize everywhere. But few external modules could be using XLOG_SEG_SIZE. Thoughts? 9. Documentation will be added in next version of patch. -- Beena Emerson On Sat, Jan 21, 2017 at 5:30 AM, Michael Paquier <michael.paqu...@gmail.com> wrote: > On Sat, Jan 21, 2017 at 4:50 AM, Robert Haas <robertmh...@gmail.com> > wrote: > > On Fri, Jan 20, 2017 at 2:34 AM, Michael Paquier > > <michael.paqu...@gmail.com> wrote: > >> On Fri, Jan 20, 2017 at 12:49 AM, Robert Haas <robertmh...@gmail.com> > wrote: > >>> On Wed, Jan 18, 2017 at 12:42 PM, Robert Haas <robertmh...@gmail.com> > wrote: > >>>> Problems 2-4 actually have to do with a DestReceiver of type > >>>> DestRemote really, really wanting to have an associated Portal and > >>>> database connection, so one approach is to create a stripped-down > >>>> DestReceiver that doesn't care about those things and then passing > >>>> that to GetPGVariable. > >>> > >>> I tried that and it worked out pretty well, so I'm inclined to go with > >>> this approach. Proposed patches attached. 0001 adds the new > >>> DestReceiver type, and 0002 is a revised patch to implement the SHOW > >>> command itself. > >>> > >>> Thoughts, comments? > >> > >> This looks like a sensible approach to me. DestRemoteSimple could be > >> useful for background workers that are not connected to a database as > >> well. Isn't there a problem with PGC_REAL parameters? > > > > No, because the output of SHOW is always of type text, regardless of > > the type of the GUC. > > Thinking about that over night, that looks pretty nice. What would be > nicer though would be to add INT8OID and BYTEAOID in the list, and > convert as well the other replication commands. At the end, I think > that we should finish by being able to remove all pq_* routine > dependencies in walsender.c, saving quite a couple of lines. > -- > Michael > -- Thank you, Beena Emerson Have a Great Day!
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