syncscan.h File Reference

#include "storage/block.h"
#include "utils/relcache.h"

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Functions
void	ss_report_location (Relation rel, BlockNumber location)
BlockNumber	ss_get_location (Relation rel, BlockNumber relnblocks)

Function Documentation

ss_get_location()

BlockNumber ss_get_location ( Relation  rel, BlockNumber  relnblocks  )

extern

Definition at line 252 of file syncscan.c.

{
    BlockNumber startloc;
 
    LWLockAcquire(SyncScanLock, LW_EXCLUSIVE);
    startloc = ss_search(rel->rd_locator, 0, false);
    LWLockRelease(SyncScanLock);
 
    /*
     * If the location is not a valid block number for this scan, start at 0.
     *
     * This can happen if for instance a VACUUM truncated the table since the
     * location was saved.
     */
    if (startloc >= relnblocks)
        startloc = 0;
 
#ifdef TRACE_SYNCSCAN
    if (trace_syncscan)
        elog(LOG,
             "SYNC_SCAN: start \"%s\" (size %u) at %u",
             RelationGetRelationName(rel), relnblocks, startloc);
#endif
 
    return startloc;
}

References elog, fb(), LOG, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), RelationData::rd_locator, RelationGetRelationName, and ss_search().

Referenced by initscan(), and table_block_parallelscan_startblock_init().

ss_report_location()

void ss_report_location ( Relation  rel, BlockNumber  location  )

extern

Definition at line 287 of file syncscan.c.

{
#ifdef TRACE_SYNCSCAN
    if (trace_syncscan)
    {
        if ((location % 1024) == 0)
            elog(LOG,
                 "SYNC_SCAN: scanning \"%s\" at %u",
                 RelationGetRelationName(rel), location);
    }
#endif
 
    /*
     * To reduce lock contention, only report scan progress every N pages. For
     * the same reason, don't block if the lock isn't immediately available.
     * Missing a few updates isn't critical, it just means that a new scan
     * that wants to join the pack will start a little bit behind the head of
     * the scan.  Hopefully the pages are still in OS cache and the scan
     * catches up quickly.
     */
    if ((location % SYNC_SCAN_REPORT_INTERVAL) == 0)
    {
        if (LWLockConditionalAcquire(SyncScanLock, LW_EXCLUSIVE))
        {
            (void) ss_search(rel->rd_locator, location, true);
            LWLockRelease(SyncScanLock);
        }
#ifdef TRACE_SYNCSCAN
        else if (trace_syncscan)
            elog(LOG,
                 "SYNC_SCAN: missed update for \"%s\" at %u",
                 RelationGetRelationName(rel), location);
#endif
    }
}

References elog, fb(), LOG, LW_EXCLUSIVE, LWLockConditionalAcquire(), LWLockRelease(), RelationData::rd_locator, RelationGetRelationName, ss_search(), and SYNC_SCAN_REPORT_INTERVAL.

Referenced by heapam_scan_sample_next_block(), heapgettup_advance_block(), and table_block_parallelscan_nextpage().