syncscan.h File Reference

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

Include dependency graph for syncscan.h:

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Go to the source code of this file.

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

Function Documentation

ss_get_location()

BlockNumber ss_get_location	(	Relation	rel,
		BlockNumber	relnblocks
	)

Definition at line 254 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(), 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
	)

Definition at line 289 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(), 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().

SyncScanShmemInit()

void SyncScanShmemInit

(

void

)

Definition at line 135 of file syncscan.c.

{
    int         i;
    bool        found;
 
    scan_locations = (ss_scan_locations_t *)
        ShmemInitStruct("Sync Scan Locations List",
                        SizeOfScanLocations(SYNC_SCAN_NELEM),
                        &found);
 
    if (!IsUnderPostmaster)
    {
        /* Initialize shared memory area */
        Assert(!found);
 
        scan_locations->head = &scan_locations->items[0];
        scan_locations->tail = &scan_locations->items[SYNC_SCAN_NELEM - 1];
 
        for (i = 0; i < SYNC_SCAN_NELEM; i++)
        {
            ss_lru_item_t *item = &scan_locations->items[i];
 
            /*
             * Initialize all slots with invalid values. As scans are started,
             * these invalid entries will fall off the LRU list and get
             * replaced with real entries.
             */
            item->location.relfilelocator.spcOid = InvalidOid;
            item->location.relfilelocator.dbOid = InvalidOid;
            item->location.relfilelocator.relNumber = InvalidRelFileNumber;
            item->location.location = InvalidBlockNumber;
 
            item->prev = (i > 0) ?
                (&scan_locations->items[i - 1]) : NULL;
            item->next = (i < SYNC_SCAN_NELEM - 1) ?
                (&scan_locations->items[i + 1]) : NULL;
        }
    }
    else
        Assert(found);
}

References Assert(), RelFileLocator::dbOid, ss_scan_locations_t::head, i, InvalidBlockNumber, InvalidOid, InvalidRelFileNumber, IsUnderPostmaster, ss_scan_locations_t::items, ss_scan_location_t::location, ss_lru_item_t::location, ss_lru_item_t::next, ss_lru_item_t::prev, ss_scan_location_t::relfilelocator, RelFileLocator::relNumber, scan_locations, ShmemInitStruct(), SizeOfScanLocations, RelFileLocator::spcOid, SYNC_SCAN_NELEM, and ss_scan_locations_t::tail.

Referenced by CreateSharedMemoryAndSemaphores().

SyncScanShmemSize()

Size SyncScanShmemSize

(

void

)

Definition at line 126 of file syncscan.c.

{
    return SizeOfScanLocations(SYNC_SCAN_NELEM);
}

References SizeOfScanLocations, and SYNC_SCAN_NELEM.

Referenced by CalculateShmemSize().