xlogstats.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * xlogstats.c
 *      Functions for WAL Statitstics
 *
 * Copyright (c) 2022-2024, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      src/backend/access/transam/xlogstats.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/xlogreader.h"
#include "access/xlogstats.h"
 
/*
 * Calculate the size of a record, split into !FPI and FPI parts.
 */
void
XLogRecGetLen(XLogReaderState *record, uint32 *rec_len,
              uint32 *fpi_len)
{
    int         block_id;
 
    /*
     * 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.
     */
    *fpi_len = 0;
    for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
    {
        if (!XLogRecHasBlockRef(record, block_id))
            continue;
 
        if (XLogRecHasBlockImage(record, block_id))
            *fpi_len += XLogRecGetBlock(record, block_id)->bimg_len;
    }
 
    /*
     * Calculate the length of the record as the total length - the length of
     * all the block images.
     */
    *rec_len = XLogRecGetTotalLen(record) - *fpi_len;
}
 
/*
 * Store per-rmgr and per-record statistics for a given record.
 */
void
XLogRecStoreStats(XLogStats *stats, XLogReaderState *record)
{
    RmgrId      rmid;
    uint8       recid;
    uint32      rec_len;
    uint32      fpi_len;
 
    Assert(stats != NULL && record != NULL);
 
    stats->count++;
 
    rmid = XLogRecGetRmid(record);
 
    XLogRecGetLen(record, &rec_len, &fpi_len);
 
    /* Update per-rmgr statistics */
 
    stats->rmgr_stats[rmid].count++;
    stats->rmgr_stats[rmid].rec_len += rec_len;
    stats->rmgr_stats[rmid].fpi_len += fpi_len;
 
    /*
     * Update per-record statistics, where the record is identified by a
     * combination of the RmgrId and the four bits of the xl_info field that
     * are the rmgr's domain (resulting in sixteen possible entries per
     * RmgrId).
     */
 
    recid = XLogRecGetInfo(record) >> 4;
 
    /*
     * XACT records need to be handled differently. Those records use the
     * first bit of those four bits for an optional flag variable and the
     * following three bits for the opcode. We filter opcode out of xl_info
     * and use it as the identifier of the record.
     */
    if (rmid == RM_XACT_ID)
        recid &= 0x07;
 
    stats->record_stats[rmid][recid].count++;
    stats->record_stats[rmid][recid].rec_len += rec_len;
    stats->record_stats[rmid][recid].fpi_len += fpi_len;
}