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Refactor the sqlite3BtreeCursorHint() interface for improved maintainability.

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FossilOrigin-Name: fc3fb5cd0d2c123a069e5b18b62bb1f708c8698a
This commit is contained in:
drh
2015-08-14 15:05:55 +00:00
parent fe66352d17
commit 0df57012da
6 changed files with 90 additions and 43 deletions
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51
src/btree.h
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@@ -150,8 +150,47 @@ int sqlite3BtreeNewDb(Btree *p);
#define BTREE_DATA_VERSION 15 /* A virtual meta-value */
/*
** Values that may be OR'd together to form the second argument of an
** sqlite3BtreeCursorHints() call.
** Kinds of hints that can be passed into the sqlite3BtreeCursorHint()
** interface.
**
** Note that cursor hints are not used by the canonical SQLite b-tree
** ayer. Cursor hints are provided so that systems that substitute their
** on custom b-tree layer can have access to additional information that might
** boost performance. Hints are only provided if SQLite is compiled with
** SQLITE_ENABLE_CURSOR_HINTS. The hinting interface is undocumented
** (except for comments such as this) and is subject to change from one
** release of SQLite to the next.
**
** BTREE_HINT_FLAGS (arguments: unsigned int)
**
** Some combinatation of BTREE_BULKLOAD and BTREE_SEEK_EQ flags. The
** argument is a single unsigned integer which overwrites all prior
** flag settings.
**
** BTREE_HINT_RANGE (arguments: Expr*, Mem*)
**
** The first argument is an Expr* (which is guaranteed to be constant for
** the lifetime of the cursor) that defines constraints on which rows
** might be fetched with this cursor. The Expr* tree may contain
** TK_REGISTER nodes that refer to values stored in the array of registers
** passed as the second parameter. In other words, if Expr.op==TK_REGISTER
** then the value of the node is the value in Mem[pExpr.iTable]. Any
** TK_COLUMN node in the expression tree refers to the Expr.iColumn-th
** column of the b-tree of the cursor. The Expr tree will not contain
** any function calls nor subqueries nor references to b-trees other than
** the cursor being hinted.
**
** The design of the _RANGE hint is aid b-tree implementations that try
** to prefetch content from remote machines - to provide those
** implementations with limits on what needs to be prefetched and thereby
** reduce network bandwidth.
*/
#define BTREE_HINT_FLAGS 1 /* Set flags indicating cursor usage */
#define BTREE_HINT_RANGE 2 /* Range constraints on queries */
/*
** Values that may be OR'd together to form the argument to the
** BTREE_HINT_FLAGS hint for sqlite3BtreeCursorHint():
**
** The BTREE_BULKLOAD flag is set on index cursors when the index is going
** to be filled with content that is already in sorted order.
@@ -165,6 +204,10 @@ int sqlite3BtreeNewDb(Btree *p);
#define BTREE_BULKLOAD 0x00000001 /* Used to full index in sorted order */
#define BTREE_SEEK_EQ 0x00000002 /* EQ seeks only - no range seeks */
#ifdef SQLITE_ENABLE_CURSOR_HINTS
void sqlite3BtreeCursorHint(BtCursor*, int, ...);
#endif
int sqlite3BtreeCursor(
Btree*, /* BTree containing table to open */
int iTable, /* Index of root page */
@@ -185,9 +228,6 @@ int sqlite3BtreeMovetoUnpacked(
);
int sqlite3BtreeCursorHasMoved(BtCursor*);
int sqlite3BtreeCursorRestore(BtCursor*, int*);
#ifdef SQLITE_ENABLE_CURSOR_HINTS
void sqlite3BtreeCursorHint(BtCursor*, int, const Expr*);
#endif
int sqlite3BtreeDelete(BtCursor*);
int sqlite3BtreeInsert(BtCursor*, const void *pKey, i64 nKey,
const void *pData, int nData,
@@ -211,7 +251,6 @@ int sqlite3BtreePutData(BtCursor*, u32 offset, u32 amt, void*);
void sqlite3BtreeIncrblobCursor(BtCursor *);
void sqlite3BtreeClearCursor(BtCursor *);
int sqlite3BtreeSetVersion(Btree *pBt, int iVersion);
void sqlite3BtreeCursorHints(BtCursor *, unsigned int mask);
#ifdef SQLITE_DEBUG
int sqlite3BtreeCursorHasHint(BtCursor*, unsigned int mask);
#endif