-// btree version 2u
+// btree version 2u sched_yield locks
// with combined latch & pool manager
-// 26 FEB 2014
+// and phase-fair reader writer lock
+// 12 MAR 2014
// author: karl malbrain, malbrain@cal.berkeley.edu
#include <stdlib.h>
#include <time.h>
#include <fcntl.h>
+#include <io.h>
#endif
#include <memory.h>
#define BT_minpage (1 << BT_minbits) // minimum page size
#define BT_maxpage (1 << BT_maxbits) // maximum page size
+// BTree page number constants
+#define ALLOC_page 0
+#define ROOT_page 1
+#define LEAF_page 2
+#define LATCH_page 3
+
+// Number of levels to create in a new BTree
+
+#define MIN_lvl 2
+#define MAX_lvl 15
+
/*
There are five lock types for each node in three independent sets:
1. (set 1) AccessIntent: Sharable. Going to Read the node. Incompatible with NodeDelete.
// definition for latch implementation
-// exclusive is set for write access
-// share is count of read accessors
-// grant write lock when share == 0
-
volatile typedef struct {
- unsigned char mutex[1];
- unsigned char exclusive:1;
- unsigned char pending:1;
- ushort share;
+ ushort lock[1];
} BtSpinLatch;
+#define XCL 1
+#define PEND 2
+#define BOTH 3
+#define SHARE 4
+
+volatile typedef struct {
+ ushort rin[1]; // readers in count
+ ushort rout[1]; // readers out count
+ ushort serving[1]; // writers out count
+ ushort ticket[1]; // writers in count
+} RWLock;
+
+// define bits at bottom of rin
+
+#define PHID 0x1 // writer phase (0/1)
+#define PRES 0x2 // writer present
+#define MASK 0x3 // both write bits
+#define RINC 0x4 // reader increment
+
// Define the length of the page and key pointers
#define BtId 6
typedef struct {
struct BtPage_ alloc[2]; // next & free page_nos in right ptr
BtSpinLatch lock[1]; // allocation area lite latch
- uint latchdeployed; // highest number of latch entries deployed
- uint nlatchpage; // number of latch pages at BT_latch
- uint latchtotal; // number of page latch entries
- uint latchhash; // number of latch hash table slots
- uint latchvictim; // next latch hash entry to examine
+ volatile uint latchdeployed;// highest number of latch entries deployed
+ volatile uint nlatchpage; // number of latch pages at BT_latch
+ volatile uint latchtotal; // number of page latch entries
+ volatile uint latchhash; // number of latch hash table slots
+ volatile uint latchvictim; // next latch hash entry to examine
+ volatile uint safelevel; // safe page level in cache
+ volatile uint cache[MAX_lvl];// cache census counts by btree level
} BtLatchMgr;
// latch hash table entries
// latch manager table structure
typedef struct {
- volatile uid page_no; // latch set page number on disk
- BtSpinLatch readwr[1]; // read/write page lock
- BtSpinLatch access[1]; // Access Intent/Page delete
- BtSpinLatch parent[1]; // Posting of fence key in parent
- volatile uint next; // next entry in hash table chain
- volatile uint prev; // prev entry in hash table chain
- volatile uint pin; // number of outstanding pins
+ volatile uid page_no; // latch set page number on disk
+ RWLock readwr[1]; // read/write page lock
+ RWLock access[1]; // Access Intent/Page delete
+ RWLock parent[1]; // Posting of fence key in parent
+ volatile ushort pin; // number of pins/level/clock bits
+ volatile uint next; // next entry in hash table chain
+ volatile uint prev; // prev entry in hash table chain
} BtLatchSet;
+#define CLOCK_mask 0xe000
+#define CLOCK_unit 0x2000
+#define PIN_mask 0x07ff
+#define LVL_mask 0x1800
+#define LVL_shift 11
+
// The object structure for Btree access
typedef struct _BtDb {
extern uint bt_tod (BtDb *bt, uint slot);
#endif
-// BTree page number constants
-#define ALLOC_page 0
-#define ROOT_page 1
-#define LEAF_page 2
-#define LATCH_page 3
-
-// Number of levels to create in a new BTree
-
-#define MIN_lvl 2
-
// The page is allocated from low and hi ends.
// The key offsets and row-id's are allocated
// from the bottom, while the text of the key
return bt->err = err;
}
-// Latch Manager
+// Phase-Fair reader/writer lock implementation
+
+void WriteLock (RWLock *lock)
+{
+ushort w, r, tix;
+
+#ifdef unix
+ tix = __sync_fetch_and_add (lock->ticket, 1);
+#else
+ tix = _InterlockedExchangeAdd16 (lock->ticket, 1);
+#endif
+ // wait for our ticket to come up
+
+ while( tix != lock->serving[0] )
+#ifdef unix
+ sched_yield();
+#else
+ SwitchToThread ();
+#endif
+
+ w = PRES | (tix & PHID);
+#ifdef unix
+ r = __sync_fetch_and_add (lock->rin, w);
+#else
+ r = _InterlockedExchangeAdd16 (lock->rin, w);
+#endif
+ while( r != *lock->rout )
+#ifdef unix
+ sched_yield();
+#else
+ SwitchToThread();
+#endif
+}
+
+void WriteRelease (RWLock *lock)
+{
+#ifdef unix
+ __sync_fetch_and_and (lock->rin, ~MASK);
+#else
+ _InterlockedAnd16 (lock->rin, ~MASK);
+#endif
+ lock->serving[0]++;
+}
+
+void ReadLock (RWLock *lock)
+{
+ushort w;
+#ifdef unix
+ w = __sync_fetch_and_add (lock->rin, RINC) & MASK;
+#else
+ w = _InterlockedExchangeAdd16 (lock->rin, RINC) & MASK;
+#endif
+ if( w )
+ while( w == (*lock->rin & MASK) )
+#ifdef unix
+ sched_yield ();
+#else
+ SwitchToThread ();
+#endif
+}
+
+void ReadRelease (RWLock *lock)
+{
+#ifdef unix
+ __sync_fetch_and_add (lock->rout, RINC);
+#else
+ _InterlockedExchangeAdd16 (lock->rout, RINC);
+#endif
+}
+
+// Spin Latch Manager
// wait until write lock mode is clear
// and add 1 to the share count
ushort prev;
do {
- // obtain latch mutex
#ifdef unix
- if( __sync_lock_test_and_set(latch->mutex, 1) )
- continue;
+ prev = __sync_fetch_and_add (latch->lock, SHARE);
#else
- if( _InterlockedExchange8(latch->mutex, 1) )
- continue;
+ prev = _InterlockedExchangeAdd16(latch->lock, SHARE);
#endif
// see if exclusive request is granted or pending
- if( prev = !(latch->exclusive | latch->pending) )
- latch->share++;
-
+ if( !(prev & BOTH) )
+ return;
#ifdef unix
- *latch->mutex = 0;
+ prev = __sync_fetch_and_add (latch->lock, -SHARE);
#else
- _InterlockedExchange8(latch->mutex, 0);
+ prev = _InterlockedExchangeAdd16(latch->lock, -SHARE);
#endif
-
- if( prev )
- return;
-
#ifdef unix
} while( sched_yield(), 1 );
#else
void bt_spinwritelock(BtSpinLatch *latch)
{
-uint prev;
+ushort prev;
do {
#ifdef unix
- if( __sync_lock_test_and_set(latch->mutex, 1) )
- continue;
+ prev = __sync_fetch_and_or(latch->lock, PEND | XCL);
#else
- if( _InterlockedExchange8(latch->mutex, 1) )
- continue;
+ prev = _InterlockedOr16(latch->lock, PEND | XCL);
#endif
- if( prev = !(latch->share | latch->exclusive) )
- latch->exclusive = 1, latch->pending = 0;
- else
- latch->pending = 1;
+ if( !(prev & XCL) )
+ if( !(prev & ~BOTH) )
+ return;
+ else
#ifdef unix
- *latch->mutex = 0;
+ __sync_fetch_and_and (latch->lock, ~XCL);
#else
- _InterlockedExchange8(latch->mutex, 0);
+ _InterlockedAnd16(latch->lock, ~XCL);
#endif
- if( prev )
- return;
#ifdef unix
} while( sched_yield(), 1 );
#else
int bt_spinwritetry(BtSpinLatch *latch)
{
-uint prev;
+ushort prev;
-#ifdef unix
- if( __sync_lock_test_and_set(latch->mutex, 1) )
- return 0;
+#ifdef unix
+ prev = __sync_fetch_and_or(latch->lock, XCL);
#else
- if( _InterlockedExchange8(latch->mutex, 1) )
- return 0;
+ prev = _InterlockedOr16(latch->lock, XCL);
#endif
// take write access if all bits are clear
- if( prev = !(latch->exclusive | latch->share) )
- latch->exclusive = 1;
-
+ if( !(prev & XCL) )
+ if( !(prev & ~BOTH) )
+ return 1;
+ else
#ifdef unix
- *latch->mutex = 0;
+ __sync_fetch_and_and (latch->lock, ~XCL);
#else
- _InterlockedExchange8(latch->mutex, 0);
+ _InterlockedAnd16(latch->lock, ~XCL);
#endif
- return prev;
+ return 0;
}
// clear write mode
void bt_spinreleasewrite(BtSpinLatch *latch)
{
#ifdef unix
- while( __sync_lock_test_and_set(latch->mutex, 1) )
- sched_yield();
-#else
- while( _InterlockedExchange8(latch->mutex, 1) )
- SwitchToThread();
-#endif
- latch->exclusive = 0;
-#ifdef unix
- *latch->mutex = 0;
+ __sync_fetch_and_and(latch->lock, ~BOTH);
#else
- _InterlockedExchange8(latch->mutex, 0);
+ _InterlockedAnd16(latch->lock, ~BOTH);
#endif
}
void bt_spinreleaseread(BtSpinLatch *latch)
{
#ifdef unix
- while( __sync_lock_test_and_set(latch->mutex, 1) )
- sched_yield();
+ __sync_fetch_and_add(latch->lock, -SHARE);
#else
- while( _InterlockedExchange8(latch->mutex, 1) )
- SwitchToThread();
-#endif
- latch->share--;
-#ifdef unix
- *latch->mutex = 0;
-#else
- _InterlockedExchange8(latch->mutex, 0);
+ _InterlockedExchangeAdd16(latch->lock, -SHARE);
#endif
}
{
BtPage page = (BtPage)((uid)slot * bt->page_size + bt->pagepool);
BtLatchSet *latch = bt->latchsets + slot;
+int lvl;
if( latch->next = bt->table[hashidx].slot )
bt->latchsets[latch->next].prev = slot;
latch->prev = 0;
latch->pin = 1;
- return bt_readpage (bt, page, page_no);
+ if( bt_readpage (bt, page, page_no) )
+ return bt->err;
+
+ lvl = page->lvl << LVL_shift;
+ if( lvl > LVL_mask )
+ lvl = LVL_mask;
+ latch->pin |= lvl; // store lvl
+ latch->pin |= lvl << 3; // initialize clock
+
+#ifdef unix
+ __sync_fetch_and_add (&bt->latchmgr->cache[page->lvl], 1);
+#else
+ _InterlockedExchangeAdd(&bt->latchmgr->cache[page->lvl], 1);
+#endif
+ return bt->err = 0;
}
// release latch pin
#ifdef unix
__sync_fetch_and_add(&latch->pin, -1);
#else
- _InterlockedDecrement (&latch->pin);
+ _InterlockedDecrement16 (&latch->pin);
#endif
}
uint hashidx = page_no % bt->latchmgr->latchhash;
BtLatchSet *latch;
uint slot, idx;
+uint lvl, cnt;
off64_t off;
uint amt[1];
BtPage page;
- // try to find unpinned entry
+ // try to find our entry
bt_spinwritelock(bt->table[hashidx].latch);
break;
} while( slot = latch->next );
- // found our entry, bring to front of hash chain
+ // found our entry
+ // increment clock
if( slot ) {
latch = bt->latchsets + slot;
+ lvl = (latch->pin & LVL_mask) >> LVL_shift;
+ lvl *= CLOCK_unit * 2;
+ lvl |= CLOCK_unit;
#ifdef unix
__sync_fetch_and_add(&latch->pin, 1);
+ __sync_fetch_and_or(&latch->pin, lvl);
#else
- _InterlockedIncrement (&latch->pin);
+ _InterlockedIncrement16 (&latch->pin);
+ _InterlockedOr16 (&latch->pin, lvl);
#endif
- // unlink our entry from its hash chain position
-
- if( latch->prev )
- bt->latchsets[latch->prev].next = latch->next;
- else
- bt->table[hashidx].slot = latch->next;
-
- if( latch->next )
- bt->latchsets[latch->next].prev = latch->prev;
-
- // now link into head of the hash chain
-
- if( latch->next = bt->table[hashidx].slot )
- bt->latchsets[latch->next].prev = slot;
-
- bt->table[hashidx].slot = slot;
- latch->prev = 0;
-
bt_spinreleasewrite(bt->table[hashidx].latch);
return latch;
}
#else
_InterlockedDecrement (&bt->latchmgr->latchdeployed);
#endif
- // find and reuse previous lru lock entry on victim hash chain
+ // find and reuse previous entry on victim
while( 1 ) {
#ifdef unix
- idx = __sync_fetch_and_add(&bt->latchmgr->latchvictim, 1);
+ slot = __sync_fetch_and_add(&bt->latchmgr->latchvictim, 1);
#else
- idx = _InterlockedIncrement (&bt->latchmgr->latchvictim) - 1;
+ slot = _InterlockedIncrement (&bt->latchmgr->latchvictim) - 1;
#endif
// try to get write lock on hash chain
// skip entry if not obtained
- // or has outstanding locks
+ // or has outstanding pins
- idx %= bt->latchmgr->latchhash;
+ slot %= bt->latchmgr->latchtotal;
- if( !bt_spinwritetry (bt->table[idx].latch) )
- continue;
+ // on slot wraparound, check census
+ // count and increment safe level
- if( slot = bt->table[idx].slot )
- while( 1 ) {
- latch = bt->latchsets + slot;
- if( !latch->next )
- break;
- slot = latch->next;
- }
+ cnt = bt->latchmgr->cache[bt->latchmgr->safelevel];
+
+ if( !slot ) {
+ if( cnt < bt->latchmgr->latchtotal / 10 )
+#ifdef unix
+ __sync_fetch_and_add(&bt->latchmgr->safelevel, 1);
+#else
+ _InterlockedIncrement (&bt->latchmgr->safelevel);
+#endif
+ continue;
+ }
+
+ latch = bt->latchsets + slot;
+ idx = latch->page_no % bt->latchmgr->latchhash;
+ lvl = (latch->pin & LVL_mask) >> LVL_shift;
- if( !slot || latch->pin ) {
- bt_spinreleasewrite (bt->table[idx].latch);
+ // see if we are evicting this level yet
+ // or if we are on same chain as hashidx
+
+ if( idx == hashidx || lvl > bt->latchmgr->safelevel )
+ continue;
+
+ if( !bt_spinwritetry (bt->table[idx].latch) )
continue;
+
+ if( latch->pin & ~LVL_mask ) {
+ if( latch->pin & CLOCK_mask )
+#ifdef unix
+ __sync_fetch_and_add(&latch->pin, -CLOCK_unit);
+#else
+ _InterlockedExchangeAdd16 (&latch->pin, -CLOCK_unit);
+#endif
+ bt_spinreleasewrite (bt->table[idx].latch);
+ continue;
}
// update permanent page area in btree
page = (BtPage)((uid)slot * bt->page_size + bt->pagepool);
-
+#ifdef unix
+ posix_fadvise (bt->idx, page_no << bt->page_bits, bt->page_size, POSIX_FADV_WILLNEED);
+ __sync_fetch_and_add (&bt->latchmgr->cache[page->lvl], -1);
+#else
+ _InterlockedExchangeAdd(&bt->latchmgr->cache[page->lvl], -1);
+#endif
if( page->dirty )
if( bt_writepage (bt, page, latch->page_no) )
return NULL;
bt = calloc (1, sizeof(BtDb));
bt->idx = open ((char*)name, O_RDWR | O_CREAT, 0666);
-
+ posix_fadvise( bt->idx, 0, 0, POSIX_FADV_RANDOM);
+
if( bt->idx == -1 ) {
fprintf(stderr, "unable to open %s\n", name);
return free(bt), NULL;
#endif
#ifdef unix
- latchmgr = malloc (BT_maxpage);
+ latchmgr = valloc (BT_maxpage);
*amt = 0;
// read minimum page size to get root info
// clear out buffer pool pages
memset(latchmgr, 0, bt->page_size);
- last = MIN_lvl;
+ last = MIN_lvl + nlatchpage;
- while( ++last < ((MIN_lvl + 1 + nlatchpage) ) )
- if( bt_writepage (bt, latchmgr->alloc, last) ) {
+ if( bt_writepage (bt, latchmgr->alloc, last) ) {
fprintf (stderr, "Unable to write buffer pool page %.8x\n", last);
return bt_close (bt), NULL;
- }
+ }
#ifdef unix
free (latchmgr);
fprintf (stderr, "Unable to mmap buffer pool, errno = %d", errno);
return bt_close (bt), NULL;
}
+ madvise (bt->table, (uid)nlatchpage << bt->page_bits, MADV_RANDOM | MADV_WILLNEED);
#else
flag = PAGE_READWRITE;
bt->halloc = CreateFileMapping(bt->idx, NULL, flag, 0, ((uid)nlatchpage + LATCH_page) * bt->page_size, NULL);
bt->latchsets = (BtLatchSet *)(bt->pagepool - (uid)bt->latchmgr->latchtotal * sizeof(BtLatchSet));
#ifdef unix
- bt->mem = malloc (2 * bt->page_size);
+ bt->mem = valloc (2 * bt->page_size);
#else
bt->mem = VirtualAlloc(NULL, 2 * bt->page_size, MEM_COMMIT, PAGE_READWRITE);
#endif
{
switch( mode ) {
case BtLockRead:
- bt_spinreadlock (latch->readwr);
+ ReadLock (latch->readwr);
break;
case BtLockWrite:
- bt_spinwritelock (latch->readwr);
+ WriteLock (latch->readwr);
break;
case BtLockAccess:
- bt_spinreadlock (latch->access);
+ ReadLock (latch->access);
break;
case BtLockDelete:
- bt_spinwritelock (latch->access);
+ WriteLock (latch->access);
break;
case BtLockParent:
- bt_spinwritelock (latch->parent);
+ WriteLock (latch->parent);
break;
}
}
{
switch( mode ) {
case BtLockRead:
- bt_spinreleaseread (latch->readwr);
+ ReadRelease (latch->readwr);
break;
case BtLockWrite:
- bt_spinreleasewrite (latch->readwr);
+ WriteRelease (latch->readwr);
break;
case BtLockAccess:
- bt_spinreleaseread (latch->access);
+ ReadRelease (latch->access);
break;
case BtLockDelete:
- bt_spinreleasewrite (latch->access);
+ WriteRelease (latch->access);
break;
case BtLockParent:
- bt_spinreleasewrite (latch->parent);
+ WriteRelease (latch->parent);
break;
}
}
uint idx, hashidx;
uid next, page_no;
BtLatchSet *latch;
+uint blks[64];
uint cnt = 0;
BtPage page;
uint amt[1];
BtKey ptr;
+#ifdef unix
+ posix_fadvise( bt->idx, 0, 0, POSIX_FADV_SEQUENTIAL);
+#endif
if( *(ushort *)(bt->latchmgr->lock) )
fprintf(stderr, "Alloc page locked\n");
*(ushort *)(bt->latchmgr->lock) = 0;
+ memset (blks, 0, sizeof(blks));
+
for( idx = 1; idx <= bt->latchmgr->latchdeployed; idx++ ) {
latch = bt->latchsets + idx;
if( *(ushort *)latch->readwr )
fprintf(stderr, "latchset %d parentlocked for page %.8x\n", idx, latch->page_no);
*(ushort *)latch->parent = 0;
- if( latch->pin ) {
+ if( latch->pin & PIN_mask ) {
fprintf(stderr, "latchset %d pinned for page %.8x\n", idx, latch->page_no);
latch->pin = 0;
}
page = (BtPage)((uid)idx * bt->page_size + bt->pagepool);
+ blks[page->lvl]++;
if( page->dirty )
if( bt_writepage (bt, page, latch->page_no) )
fprintf(stderr, "Page %.8x Write Error\n", latch->page_no);
}
+ for( idx = 0; blks[idx]; idx++ )
+ fprintf(stderr, "cache: %d lvl %d blocks\n", blks[idx], idx);
+
for( hashidx = 0; hashidx < bt->latchmgr->latchhash; hashidx++ ) {
if( *(ushort *)(bt->table[hashidx].latch) )
fprintf(stderr, "hash entry %d locked\n", hashidx);
*(ushort *)(bt->table[hashidx].latch) = 0;
-
- if( idx = bt->table[hashidx].slot ) do {
- latch = bt->latchsets + idx;
- if( latch->pin )
- fprintf(stderr, "latchset %d pinned for page %.8x\n", idx, latch->page_no);
- } while( idx = latch->next );
}
+ memset (blks, 0, sizeof(blks));
+
next = bt->latchmgr->nlatchpage + LATCH_page;
page_no = LEAF_page;
}
if( !bt->frame->lvl )
cnt += bt->frame->act;
+ blks[bt->frame->lvl]++;
}
if( page_no > LEAF_page )
next = page_no + 1;
page_no = next;
}
+
+ for( idx = 0; blks[idx]; idx++ )
+ fprintf(stderr, "btree: %d lvl %d blocks\n", blks[idx], idx);
+
return cnt - 1;
}
unsigned char key[256];
double done, start;
uid next, page_no;
+BtLatchSet *latch;
float elapsed;
time_t tod[1];
uint scan = 0;
uint len = 0;
uint map = 0;
+BtPage page;
BtKey ptr;
BtDb *bt;
FILE *in;
+#ifdef WIN32
+ _setmode (1, _O_BINARY);
+#endif
if( argc < 4 ) {
fprintf (stderr, "Usage: %s idx_file src_file Read/Write/Scan/Delete/Find/Count [page_bits mapped_pool_pages start_line_number]\n", argv[0]);
fprintf (stderr, " page_bits: size of btree page in bits\n");
switch(argv[3][0]| 0x20)
{
- case 'a':
- fprintf(stderr, "started audit for %s\n", argv[2]);
+ case 'p': // display page
+ if( latch = bt_pinlatch (bt, off) )
+ page = bt_mappage (bt, latch);
+ else
+ fprintf(stderr, "unable to read page %.8x\n", off);
+
+ write (1, page, bt->page_size);
+ break;
+
+ case 'a': // buffer pool audit
+ fprintf(stderr, "started audit for %s\n", argv[1]);
cnt = bt_audit (bt);
- fprintf(stderr, "finished audit for %s, %d keys\n", argv[2], cnt);
+ fprintf(stderr, "finished audit for %s, %d keys\n", argv[1], cnt);
break;
- case 'w':
+ case 'w': // write keys
fprintf(stderr, "started indexing for %s\n", argv[2]);
- if( argc > 2 && (in = fopen (argv[2], "rb")) )
+ if( argc > 2 && (in = fopen (argv[2], "rb")) ) {
+#ifdef unix
+ posix_fadvise( fileno(in), 0, 0, POSIX_FADV_NOREUSE);
+#endif
while( ch = getc(in), ch != EOF )
if( ch == '\n' )
{
}
else if( len < 245 )
key[len++] = ch;
+ }
fprintf(stderr, "finished adding keys for %s, %d \n", argv[2], line);
break;
- case 'd':
+ case 'd': // delete keys
fprintf(stderr, "started deleting keys for %s\n", argv[2]);
- if( argc > 2 && (in = fopen (argv[2], "rb")) )
+ if( argc > 2 && (in = fopen (argv[2], "rb")) ) {
+#ifdef unix
+ posix_fadvise( fileno(in), 0, 0, POSIX_FADV_NOREUSE);
+#endif
while( ch = getc(in), ch != EOF )
if( ch == '\n' )
{
}
else if( len < 245 )
key[len++] = ch;
+ }
fprintf(stderr, "finished deleting keys for %s, %d \n", argv[2], line);
break;
- case 'f':
+ case 'f': // find keys
fprintf(stderr, "started finding keys for %s\n", argv[2]);
- if( argc > 2 && (in = fopen (argv[2], "rb")) )
+ if( argc > 2 && (in = fopen (argv[2], "rb")) ) {
+#ifdef unix
+ posix_fadvise( fileno(in), 0, 0, POSIX_FADV_NOREUSE);
+#endif
while( ch = getc(in), ch != EOF )
if( ch == '\n' )
{
}
else if( len < 245 )
key[len++] = ch;
+ }
fprintf(stderr, "finished search of %d keys for %s, found %d\n", line, argv[2], found);
break;
- case 's':
+ case 's': // scan and print keys
fprintf(stderr, "started scaning\n");
cnt = len = key[0] = 0;
fprintf(stderr, " Total keys read %d\n", cnt - 1);
break;
- case 'c':
+ case 'c': // count keys
fprintf(stderr, "started counting\n");
cnt = 0;
page_no = LEAF_page;
while( page_no < bt_getid(bt->latchmgr->alloc->right) ) {
- BtLatchSet *latch;
- BtPage page;
if( latch = bt_pinlatch (bt, page_no) )
page = bt_mappage (bt, latch);
if( !page->free && !page->lvl )
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