PostgreSQL Source Code git master
Functions
syncscan.h File Reference
#include "storage/block.h"
#include "utils/relcache.h"
Include dependency graph for syncscan.h:
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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.

255{
256 BlockNumber startloc;
257
258 LWLockAcquire(SyncScanLock, LW_EXCLUSIVE);
259 startloc = ss_search(rel->rd_locator, 0, false);
260 LWLockRelease(SyncScanLock);
261
262 /*
263 * If the location is not a valid block number for this scan, start at 0.
264 *
265 * This can happen if for instance a VACUUM truncated the table since the
266 * location was saved.
267 */
268 if (startloc >= relnblocks)
269 startloc = 0;
270
271#ifdef TRACE_SYNCSCAN
272 if (trace_syncscan)
273 elog(LOG,
274 "SYNC_SCAN: start \"%s\" (size %u) at %u",
275 RelationGetRelationName(rel), relnblocks, startloc);
276#endif
277
278 return startloc;
279}
uint32 BlockNumber
Definition: block.h:31
#define LOG
Definition: elog.h:31
#define elog(elevel,...)
Definition: elog.h:226
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1174
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1894
@ LW_EXCLUSIVE
Definition: lwlock.h:112
#define RelationGetRelationName(relation)
Definition: rel.h:548
RelFileLocator rd_locator
Definition: rel.h:57
static BlockNumber ss_search(RelFileLocator relfilelocator, BlockNumber location, bool set)
Definition: syncscan.c:191

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.

290{
291#ifdef TRACE_SYNCSCAN
292 if (trace_syncscan)
293 {
294 if ((location % 1024) == 0)
295 elog(LOG,
296 "SYNC_SCAN: scanning \"%s\" at %u",
297 RelationGetRelationName(rel), location);
298 }
299#endif
300
301 /*
302 * To reduce lock contention, only report scan progress every N pages. For
303 * the same reason, don't block if the lock isn't immediately available.
304 * Missing a few updates isn't critical, it just means that a new scan
305 * that wants to join the pack will start a little bit behind the head of
306 * the scan. Hopefully the pages are still in OS cache and the scan
307 * catches up quickly.
308 */
309 if ((location % SYNC_SCAN_REPORT_INTERVAL) == 0)
310 {
311 if (LWLockConditionalAcquire(SyncScanLock, LW_EXCLUSIVE))
312 {
313 (void) ss_search(rel->rd_locator, location, true);
314 LWLockRelease(SyncScanLock);
315 }
316#ifdef TRACE_SYNCSCAN
317 else if (trace_syncscan)
318 elog(LOG,
319 "SYNC_SCAN: missed update for \"%s\" at %u",
320 RelationGetRelationName(rel), location);
321#endif
322 }
323}
bool LWLockConditionalAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1345
#define SYNC_SCAN_REPORT_INTERVAL
Definition: syncscan.c:83

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.

136{
137 int i;
138 bool found;
139
141 ShmemInitStruct("Sync Scan Locations List",
143 &found);
144
146 {
147 /* Initialize shared memory area */
148 Assert(!found);
149
152
153 for (i = 0; i < SYNC_SCAN_NELEM; i++)
154 {
156
157 /*
158 * Initialize all slots with invalid values. As scans are started,
159 * these invalid entries will fall off the LRU list and get
160 * replaced with real entries.
161 */
166
167 item->prev = (i > 0) ?
168 (&scan_locations->items[i - 1]) : NULL;
169 item->next = (i < SYNC_SCAN_NELEM - 1) ?
170 (&scan_locations->items[i + 1]) : NULL;
171 }
172 }
173 else
174 Assert(found);
175}
#define InvalidBlockNumber
Definition: block.h:33
bool IsUnderPostmaster
Definition: globals.c:120
Assert(PointerIsAligned(start, uint64))
i
int i
Definition: isn.c:77
#define InvalidOid
Definition: postgres_ext.h:37
#define InvalidRelFileNumber
Definition: relpath.h:26
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:387
RelFileNumber relNumber
Definition: relfilelocator.h:62
Definition: syncscan.c:98
ss_scan_location_t location
Definition: syncscan.c:101
struct ss_lru_item_t * next
Definition: syncscan.c:100
struct ss_lru_item_t * prev
Definition: syncscan.c:99
RelFileLocator relfilelocator
Definition: syncscan.c:93
BlockNumber location
Definition: syncscan.c:94
Definition: syncscan.c:105
ss_lru_item_t * head
Definition: syncscan.c:106
ss_lru_item_t items[FLEXIBLE_ARRAY_MEMBER]
Definition: syncscan.c:108
ss_lru_item_t * tail
Definition: syncscan.c:107
static ss_scan_locations_t * scan_locations
Definition: syncscan.c:115
#define SYNC_SCAN_NELEM
Definition: syncscan.c:71
#define SizeOfScanLocations(N)
Definition: syncscan.c:111

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 CreateOrAttachShmemStructs().

◆ SyncScanShmemSize()

Size SyncScanShmemSize ( void  )

Definition at line 126 of file syncscan.c.

127{
129}

References SizeOfScanLocations, and SYNC_SCAN_NELEM.

Referenced by CalculateShmemSize().

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