src/backend/access/transam/xlogstats.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * xlogstats.c
   4  *              Functions for WAL Statitstics
   5  *
   6  * Copyright (c) 2022-2025, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *              src/backend/access/transam/xlogstats.c
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #include "postgres.h"
  14
  15 #include "access/xlogreader.h"
  16 #include "access/xlogstats.h"
  17
  18 /*
  19  * Calculate the size of a record, split into !FPI and FPI parts.
  20  */
  21 void
  22 XLogRecGetLen(XLogReaderState *record, uint32 *rec_len,
  23                           uint32 *fpi_len)
  24 {
  25         int                     block_id;
  26
  27         /*
  28          * Calculate the amount of FPI data in the record.
  29          *
  30          * XXX: We peek into xlogreader's private decoded backup blocks for the
  31          * bimg_len indicating the length of FPI data.
  32          */
  33         *fpi_len = 0;
  34         for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
  35         {
  36                 if (!XLogRecHasBlockRef(record, block_id))
  37                         continue;
  38
  39                 if (XLogRecHasBlockImage(record, block_id))
  40                         *fpi_len += XLogRecGetBlock(record, block_id)->bimg_len;
  41         }
  42
  43         /*
  44          * Calculate the length of the record as the total length - the length of
  45          * all the block images.
  46          */
  47         *rec_len = XLogRecGetTotalLen(record) - *fpi_len;
  48 }
  49
  50 /*
  51  * Store per-rmgr and per-record statistics for a given record.
  52  */
  53 void
  54 XLogRecStoreStats(XLogStats *stats, XLogReaderState *record)
  55 {
  56         RmgrId          rmid;
  57         uint8           recid;
  58         uint32          rec_len;
  59         uint32          fpi_len;
  60
  61         Assert(stats != NULL && record != NULL);
  62
  63         stats->count++;
  64
  65         rmid = XLogRecGetRmid(record);
  66
  67         XLogRecGetLen(record, &rec_len, &fpi_len);
  68
  69         /* Update per-rmgr statistics */
  70
  71         stats->rmgr_stats[rmid].count++;
  72         stats->rmgr_stats[rmid].rec_len += rec_len;
  73         stats->rmgr_stats[rmid].fpi_len += fpi_len;
  74
  75         /*
  76          * Update per-record statistics, where the record is identified by a
  77          * combination of the RmgrId and the four bits of the xl_info field that
  78          * are the rmgr's domain (resulting in sixteen possible entries per
  79          * RmgrId).
  80          */
  81
  82         recid = XLogRecGetInfo(record) >> 4;
  83
  84         /*
  85          * XACT records need to be handled differently. Those records use the
  86          * first bit of those four bits for an optional flag variable and the
  87          * following three bits for the opcode. We filter opcode out of xl_info
  88          * and use it as the identifier of the record.
  89          */
  90         if (rmid == RM_XACT_ID)
  91                 recid &= 0x07;
  92
  93         stats->record_stats[rmid][recid].count++;
  94         stats->record_stats[rmid][recid].rec_len += rec_len;
  95         stats->record_stats[rmid][recid].fpi_len += fpi_len;
  96 }