database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-08-07 02:42:48 +03:00
Code Activity

Provide hints to the btree layer Next and Previous primitives to let them

Browse Source 
know if they can be no-ops if the underlying index is unique.

FossilOrigin-Name: 6c643e45c274e755dc5a1a65673df79261c774be
This commit is contained in:
drh
2014-02-03 14:04:11 +00:00
parent 6645370e5b
commit e39a732ce2
6 changed files with 62 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
src/btree.c
View File

@@ -4777,6 +4777,15 @@ int sqlite3BtreeEof(BtCursor *pCur){
** successful then set *pRes=0. If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.
**
** The calling function will set *pRes to 0 or 1. The initial *pRes value
** will be 1 if the cursor being stepped corresponds to an SQL index and
** if this routine could have been skipped if that SQL index had been
** a unique index. Otherwise the caller will have set *pRes to zero.
** Zero is the common case. The btree implementation is free to use the
** initial *pRes value as a hint to improve performance, but the current
** SQLite btree implementation does not. (Note that the comdb2 btree
** implementation does use this hint, however.)
*/
int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
int rc;
@@ -4785,6 +4794,7 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
assert( cursorHoldsMutex(pCur) );
assert( pRes!=0 );
assert( *pRes==0 || *pRes==1 );
assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
if( pCur->eState!=CURSOR_VALID ){
rc = restoreCursorPosition(pCur);
@@ -4863,6 +4873,15 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
** successful then set *pRes=0. If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.
**
** The calling function will set *pRes to 0 or 1. The initial *pRes value
** will be 1 if the cursor being stepped corresponds to an SQL index and
** if this routine could have been skipped if that SQL index had been
** a unique index. Otherwise the caller will have set *pRes to zero.
** Zero is the common case. The btree implementation is free to use the
** initial *pRes value as a hint to improve performance, but the current
** SQLite btree implementation does not. (Note that the comdb2 btree
** implementation does use this hint, however.)
*/
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
int rc;
@@ -4870,6 +4889,7 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
assert( cursorHoldsMutex(pCur) );
assert( pRes!=0 );
assert( *pRes==0 || *pRes==1 );
assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
pCur->atLast = 0;
if( pCur->eState!=CURSOR_VALID ){
@@ -7096,7 +7116,7 @@ int sqlite3BtreeDelete(BtCursor *pCur){
** sub-tree headed by the child page of the cell being deleted. This makes
** balancing the tree following the delete operation easier. */
if( !pPage->leaf ){
int notUsed;
int notUsed = 0;
rc = sqlite3BtreePrevious(pCur, &notUsed);
if( rc ) return rc;
}