BUG #14687: pg_xlogdump does only count "main data" for record length and leading to incorrect statistics

The following bug has been logged on the website:

Bug reference:      14687
Logged by:          Chen huajun
Email address:      chjischj@163.com
PostgreSQL version: 9.5.0
Operating system:   ALL
Description:        

Currently, record length in pg_xlogdump/pg_waldump's output only count
length of "main data",
This results in pg_xlogdump/pg_waldump can not accurately count the size of
the various types of WAL records.

for example

    [postgres@node1 ~]$ pg_waldump --stats=record
pg10data/pg_wal/00000001000000000000001F
    Type                                           N      (%)         
Record size      (%)             FPI size      (%)        Combined size     
(%)
    ----                                           -      ---         
-----------      ---             --------      ---        -------------     
---
    XLOG/FPI                                     939 ( 34.68)               
22536 ( 27.15)              6897764 ( 99.75)              6920300 ( 98.89)
    Transaction/COMMIT                             6 (  0.22)               
  976 (  1.18)                    0 (  0.00)                  976 (  0.01)
    Storage/CREATE                                 3 (  0.11)               
  120 (  0.14)                    0 (  0.00)                  120 (  0.00)
    Standby/LOCK                                   6 (  0.22)               
  240 (  0.29)                    0 (  0.00)                  240 (  0.00)
    Standby/INVALIDATIONS                          3 (  0.11)               
  264 (  0.32)                    0 (  0.00)                  264 (  0.00)
    Heap2/VISIBLE                                  1 (  0.04)               
   29 (  0.03)                 8192 (  0.12)                 8221 (  0.12)
    Heap2/MULTI_INSERT                           165 (  6.09)               
14606 ( 17.60)                    0 (  0.00)                14606 (  0.21)
    Heap2/MULTI_INSERT+INIT                     1493 ( 55.13)               
41804 ( 50.37)                    0 (  0.00)                41804 (  0.60)
    Heap/INSERT                                   29 (  1.07)               
  783 (  0.94)                    0 (  0.00)                  783 (  0.01)
    Heap/INPLACE                                   7 (  0.26)               
  182 (  0.22)                    0 (  0.00)                  182 (  0.00)
    Btree/INSERT_LEAF                             56 (  2.07)               
 1456 (  1.75)                 8888 (  0.13)                10344 (  0.15)
                                            --------                     
--------                      --------                      --------
    Total                                       2708                        
82996 [1.19%]               6914844 [98.81%]              6997840 [100%]

Total Combined size above is only 6997840 byte,but should be 16MB.


So, I modified one line of code in pg_waldump.c

src/bin/pg_waldump/pg_waldump.c:390

        rec_len = XLogRecGetDataLen(record) + SizeOfXLogRecord;

        /*
         * Calculate the amount of FPI data in the record.
         *
         * XXX: We peek into xlogreader's private decoded backup blocks for
the
         * bimg_len indicating the length of FPI data. It doesn't seem worth
it to
         * add an accessor macro for this.
         */
        fpi_len = 0;
        for (block_id = 0; block_id <= record->max_block_id; block_id++)
        {
                if (XLogRecHasBlockImage(record, block_id))
                        fpi_len += record->blocks[block_id].bimg_len;
        }
==>
        
        /*
         * Calculate the amount of FPI data in the record.
         *
         * XXX: We peek into xlogreader's private decoded backup blocks for
the
         * bimg_len indicating the length of FPI data. It doesn't seem worth
it to
         * add an accessor macro for this.
         */
        fpi_len = 0;
        for (block_id = 0; block_id <= record->max_block_id; block_id++)
        {
                if (XLogRecHasBlockImage(record, block_id))
                        fpi_len += record->blocks[block_id].bimg_len;
        }
        rec_len = XLogRecGetTotalLen(record) - fpi_len;
        

and got more precise output(correct FPI ratio is 41.37% instead of 98.81%)

    [postgres@node1 ~]$ pg_waldump  --stats=record
pg10data/pg_wal/00000001000000000000001F
    Type                                           N      (%)         
Record size      (%)             FPI size      (%)        Combined size     
(%)
    ----                                           -      ---         
-----------      ---             --------      ---        -------------     
---
    XLOG/FPI                                     939 ( 34.68)               
46011 (  0.47)              6897764 ( 99.75)              6943775 ( 41.54)
    Transaction/COMMIT                             6 (  0.22)               
  988 (  0.01)                    0 (  0.00)                  988 (  0.01)
    Storage/CREATE                                 3 (  0.11)               
  126 (  0.00)                    0 (  0.00)                  126 (  0.00)
    Standby/LOCK                                   6 (  0.22)               
  252 (  0.00)                    0 (  0.00)                  252 (  0.00)
    Standby/INVALIDATIONS                          3 (  0.11)               
  270 (  0.00)                    0 (  0.00)                  270 (  0.00)
    Heap2/VISIBLE                                  1 (  0.04)               
   64 (  0.00)                 8192 (  0.12)                 8256 (  0.05)
    Heap2/MULTI_INSERT                           165 (  6.09)              
547329 (  5.59)                    0 (  0.00)               547329 ( 
3.27)
    Heap2/MULTI_INSERT+INIT                     1493 ( 55.13)             
9194033 ( 93.82)                    0 (  0.00)              9194033 (
55.01)
    Heap/INSERT                                   29 (  1.07)               
 5655 (  0.06)                    0 (  0.00)                 5655 (  0.03)
    Heap/INPLACE                                   7 (  0.26)               
 1493 (  0.02)                    0 (  0.00)                 1493 (  0.01)
    Btree/INSERT_LEAF                             56 (  2.07)               
 3723 (  0.04)                 8888 (  0.13)                12611 (  0.08)
                                            --------                     
--------                      --------                      --------
    Total                                       2708                      
9799944 [58.63%]              6914844 [41.37%]             16714788 [100%]