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author
Artur Zakirov
committed
Added comments to rumget.c
1 parent 353ea47 commit 6b8b942

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3 files changed

+93
-30
lines changed

3 files changed

+93
-30
lines changed

‎rum.h

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -259,9 +259,9 @@ typedef signed char RumNullCategory;
259259

260260
typedef struct
261261
{
262-
ItemPointerData iptr;
263-
OffsetNumber offsetNumer;
264-
uint16 pageOffset;
262+
ItemPointerData iptr;
263+
OffsetNumber offsetNumer;
264+
uint16 pageOffset;
265265
} RumDataLeafItemIndex;
266266

267267
#define RumDataLeafIndexCount 32

‎rumbtree.c

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -72,6 +72,10 @@ rumPrepareFindLeafPage(RumBtree btree, BlockNumber blkno)
7272
RumBtreeStack *
7373
rumReFindLeafPage(RumBtree btree, RumBtreeStack *stack)
7474
{
75+
/*
76+
* Traverse the tree upwards until we sure that requested leaf page is
77+
* in this subtree. Or we can stop at root page.
78+
*/
7579
while (stack->parent)
7680
{
7781
RumBtreeStack *ptr;
@@ -90,6 +94,11 @@ rumReFindLeafPage(RumBtree btree, RumBtreeStack *stack)
9094
page = BufferGetPage(stack->buffer);
9195
maxoff = RumPageGetOpaque(page)->maxoff;
9296

97+
/*
98+
* We don't know right bound of rightmost pointer. So, we can be sure
99+
* that requested leaf page is in this subtree only when requested item
100+
* pointer is less than item pointer previous to rightmost.
101+
*/
93102
if (rumCompareItemPointers(
94103
&(((PostingItem *)RumDataPageGetItem(page, maxoff - 1))->key),
95104
&btree->items[btree->curitem].iptr) >= 0)
@@ -98,6 +107,7 @@ rumReFindLeafPage(RumBtree btree, RumBtreeStack *stack)
98107
}
99108
}
100109

110+
/* Traverse tree downwards. */
101111
stack = rumFindLeafPage(btree, stack);
102112
return stack;
103113
}

‎rumget.c

Lines changed: 80 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -80,14 +80,14 @@ callConsistentFn(RumState *rumstate, RumScanKey key)
8080

8181
if (res && key->attnum == rumstate->attrnAddToColumn)
8282
{
83-
int i;
83+
uint32 i;
8484

8585
/* remember some addinfo value for later ordering by addinfo
8686
from another column */
8787

8888
key->outerAddInfoIsNull = true;
8989

90-
for(i=0; i<key->nuserentries; i++)
90+
for(i = 0; i < key->nuserentries; i++)
9191
{
9292
if (key->entryRes[i] && key->addInfoIsNull[0] == false)
9393
{
@@ -571,6 +571,10 @@ startScanKey(RumState *rumstate, RumScanKey key)
571571
key->isFinished = false;
572572
}
573573

574+
/*
575+
* Compare entries position. At first consider isFinished flag, then compare
576+
* item pointers.
577+
*/
574578
static int
575579
cmpEntries(RumScanEntry e1, RumScanEntry e2)
576580
{
@@ -670,6 +674,10 @@ startScan(IndexScanDesc scan)
670674

671675
if (useFastScan)
672676
{
677+
/*
678+
* We are going to use fast scan. Do some preliminaries. Start scan
679+
* of each entry and sort entries by descending item pointers.
680+
*/
673681
so->sortedEntries = (RumScanEntry *)palloc(sizeof(RumScanEntry) *
674682
so->totalentries);
675683
memcpy(so->sortedEntries, so->entries, sizeof(RumScanEntry) *
@@ -1237,15 +1245,21 @@ scanGetItemRegular(IndexScanDesc scan, ItemPointer advancePast,
12371245
return TRUE;
12381246
}
12391247

1248+
/*
1249+
* Finds part of page containing requested item using small index at the end
1250+
* of page.
1251+
*/
12401252
static bool
1241-
scanPage(RumState *rumstate, RumScanEntry entry, ItemPointer item, Page page, bool equalOk)
1253+
scanPage(RumState *rumstate, RumScanEntry entry, ItemPointer item, Page page,
1254+
bool equalOk)
12421255
{
1243-
int j;
1256+
int j;
12441257
RumKey iter_item;
1245-
Pointer ptr;
1246-
OffsetNumber first = FirstOffsetNumber, i, maxoff;
1247-
bool found;
1248-
int cmp;
1258+
Pointer ptr;
1259+
OffsetNumber first = FirstOffsetNumber,
1260+
i, maxoff;
1261+
bool found;
1262+
int cmp;
12491263

12501264
ItemPointerSetMin(&iter_item.iptr);
12511265

@@ -1300,6 +1314,9 @@ scanPage(RumState *rumstate, RumScanEntry entry, ItemPointer item, Page page, bo
13001314
return true;
13011315
}
13021316

1317+
/*
1318+
* Find item pointer of entry with is greater or equal to given item pointer.
1319+
*/
13031320
static void
13041321
entryFindItem(RumState *rumstate, RumScanEntry entry, RumKey *item)
13051322
{
@@ -1311,6 +1328,7 @@ entryFindItem(RumState *rumstate, RumScanEntry entry, RumKey *item)
13111328
return;
13121329
}
13131330

1331+
/* Try to find in loaded part of page */
13141332
if (rumCompareItemPointers(&entry->list[entry->nlist - 1].iptr,
13151333
&item->iptr) >= 0)
13161334
{
@@ -1329,13 +1347,13 @@ entryFindItem(RumState *rumstate, RumScanEntry entry, RumKey *item)
13291347
}
13301348
}
13311349

1332-
13331350
if (!BufferIsValid(entry->buffer))
13341351
{
13351352
entry->isFinished = TRUE;
13361353
return;
13371354
}
13381355

1356+
/* Check rest of page */
13391357
LockBuffer(entry->buffer, RUM_SHARE);
13401358

13411359
if (scanPage(rumstate, entry, &item->iptr,
@@ -1346,6 +1364,7 @@ entryFindItem(RumState *rumstate, RumScanEntry entry, RumKey *item)
13461364
return;
13471365
}
13481366

1367+
/* Try to traverse to another leaf page */
13491368
entry->gdi->btree.items = item;
13501369
entry->gdi->btree.curitem = 0;
13511370

@@ -1363,6 +1382,7 @@ entryFindItem(RumState *rumstate, RumScanEntry entry, RumKey *item)
13631382
return;
13641383
}
13651384

1385+
/* At last try to traverse by right links */
13661386
for (;;)
13671387
{
13681388
/*
@@ -1402,17 +1422,20 @@ entryFindItem(RumState *rumstate, RumScanEntry entry, RumKey *item)
14021422
}
14031423
}
14041424

1425+
/*
1426+
* Do preConsistent check for all the key where applicable.
1427+
*/
14051428
static bool
14061429
preConsistentCheck(RumScanOpaque so)
14071430
{
1408-
RumState *rumstate = &so->rumstate;
1409-
int i, j;
1410-
bool recheck;
1431+
RumState *rumstate = &so->rumstate;
1432+
uint32 i, j;
1433+
bool recheck;
14111434

14121435
for (j = 0; j < so->nkeys; j++)
14131436
{
1414-
RumScanKey key = &so->keys[j];
1415-
bool hasFalse = false;
1437+
RumScanKey key = &so->keys[j];
1438+
bool hasFalse = false;
14161439

14171440
if (key->orderBy)
14181441
continue;
@@ -1448,29 +1471,43 @@ preConsistentCheck(RumScanOpaque so)
14481471
return true;
14491472
}
14501473

1474+
/*
1475+
* Shift value of some entry which index in so->sortedEntries is equal or greater
1476+
* to i.
1477+
*/
14511478
static void
14521479
entryShift(int i, RumScanOpaque so, bool find)
14531480
{
1454-
int minIndex = -1, j;
1455-
uint32 minPredictNumberResult = 0;
1481+
int minIndex = -1,
1482+
j;
1483+
uint32 minPredictNumberResult = 0;
14561484
RumState *rumstate = &so->rumstate;
14571485

1486+
/*
1487+
* It's more efficient to move entry with smallest posting list/tree. So
1488+
* find one.
1489+
*/
14581490
for (j = i; j < so->totalentries; j++)
14591491
{
1460-
if (minIndex < 0 || so->sortedEntries[j]->predictNumberResult < minPredictNumberResult)
1492+
if (minIndex < 0 ||
1493+
so->sortedEntries[j]->predictNumberResult < minPredictNumberResult)
14611494
{
14621495
minIndex = j;
14631496
minPredictNumberResult = so->sortedEntries[j]->predictNumberResult;
14641497
}
14651498
}
14661499

1500+
/* Do shift of required type */
14671501
if (find)
1468-
entryFindItem(rumstate, so->sortedEntries[minIndex], &so->sortedEntries[i - 1]->curItem);
1502+
entryFindItem(rumstate, so->sortedEntries[minIndex],
1503+
&so->sortedEntries[i - 1]->curItem);
14691504
else if (!so->sortedEntries[minIndex]->isFinished)
14701505
entryGetItem(rumstate, so->sortedEntries[minIndex]);
14711506

1507+
/* Restore order of so->sortedEntries */
14721508
while (minIndex > 0 &&
1473-
cmpEntries(so->sortedEntries[minIndex], so->sortedEntries[minIndex - 1]) > 0)
1509+
cmpEntries(so->sortedEntries[minIndex],
1510+
so->sortedEntries[minIndex - 1]) > 0)
14741511
{
14751512
RumScanEntry tmp;
14761513
tmp = so->sortedEntries[minIndex];
@@ -1480,13 +1517,16 @@ entryShift(int i, RumScanOpaque so, bool find)
14801517
}
14811518
}
14821519

1520+
/*
1521+
* Get next item pointer using fast scan.
1522+
*/
14831523
static bool
14841524
scanGetItemFast(IndexScanDesc scan, ItemPointer advancePast,
1485-
ItemPointerData *item, bool *recheck)
1525+
ItemPointerData *item, bool *recheck)
14861526
{
14871527
RumScanOpaque so = (RumScanOpaque) scan->opaque;
1488-
int i, j, k;
1489-
bool preConsistentFalse, consistentFalse;
1528+
int i, j, k;
1529+
bool preConsistentFalse, consistentFalse;
14901530

14911531
if (so->entriesIncrIndex >= 0)
14921532
{
@@ -1496,6 +1536,10 @@ scanGetItemFast(IndexScanDesc scan, ItemPointer advancePast,
14961536

14971537
for (;;)
14981538
{
1539+
/*
1540+
* Our entries is ordered by descending of item pointers.
1541+
* The first goal is to find border where preConsistent becomes false.
1542+
*/
14991543
preConsistentFalse = false;
15001544
j = 0;
15011545
k = 0;
@@ -1517,6 +1561,10 @@ scanGetItemFast(IndexScanDesc scan, ItemPointer advancePast,
15171561
}
15181562
}
15191563

1564+
/*
1565+
* If we found false in preConsistent then we can safely move entries
1566+
* which was true in preConsistent argument.
1567+
*/
15201568
if (so->sortedEntries[i - 1]->isFinished == TRUE)
15211569
return false;
15221570

@@ -1526,6 +1574,7 @@ scanGetItemFast(IndexScanDesc scan, ItemPointer advancePast,
15261574
continue;
15271575
}
15281576

1577+
/* Call consistent method */
15291578
consistentFalse = false;
15301579
for (i = 0; i < so->nkeys; i++)
15311580
{
@@ -1563,6 +1612,7 @@ scanGetItemFast(IndexScanDesc scan, ItemPointer advancePast,
15631612
if (consistentFalse)
15641613
continue;
15651614

1615+
/* Calculate recheck from each key */
15661616
*recheck = false;
15671617
for (i = 0; i < so->nkeys; i++)
15681618
{
@@ -1586,6 +1636,9 @@ scanGetItemFast(IndexScanDesc scan, ItemPointer advancePast,
15861636
return false;
15871637
}
15881638

1639+
/*
1640+
* Get next item whether using regular or fast scan.
1641+
*/
15891642
static bool
15901643
scanGetItem(IndexScanDesc scan, ItemPointer advancePast,
15911644
ItemPointerData *item, bool *recheck)
@@ -1776,7 +1829,7 @@ collectMatchesForHeapRow(IndexScanDesc scan, pendingPosition *pos)
17761829
OffsetNumber attrnum;
17771830
Page page;
17781831
IndexTuple itup;
1779-
int i,
1832+
uint32 i,
17801833
j;
17811834

17821835
/*
@@ -1997,7 +2050,7 @@ scanPendingInsert(IndexScanDesc scan)
19972050
MemoryContext oldCtx;
19982051
bool recheck,
19992052
match;
2000-
int i;
2053+
uint32 i;
20012054
pendingPosition pos;
20022055
Buffer metabuffer = ReadBuffer(scan->indexRelation, RUM_METAPAGE_BLKNO);
20032056
BlockNumber blkno;
@@ -2145,7 +2198,7 @@ keyGetOrdering(RumState *rumstate, MemoryContext tempCtx, RumScanKey key,
21452198
ItemPointer iptr)
21462199
{
21472200
RumScanEntry entry;
2148-
int i;
2201+
uint32 i;
21492202

21502203
if (key->useAddToColumn)
21512204
{
@@ -2200,7 +2253,7 @@ static void
22002253
insertScanItem(RumScanOpaque so, bool recheck)
22012254
{
22022255
RumSortItem *item;
2203-
int i, j;
2256+
uint32 i, j;
22042257

22052258
item = (RumSortItem *)
22062259
MemoryContextAlloc(rum_tuplesort_get_memorycontext(so->sortstate),
@@ -2297,7 +2350,7 @@ rumgettuple(IndexScanDesc scan, ScanDirection direction)
22972350
item = rum_tuplesort_getrum(so->sortstate, true, &should_free);
22982351
if (item)
22992352
{
2300-
int i, j = 0;
2353+
uint32 i, j = 0;
23012354

23022355
scan->xs_ctup.t_self = item->iptr;
23032356
scan->xs_recheck = item->recheck;

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