*** 119,151 ****
int (*xOpen)(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor);
----
*xClose*
int (*xClose)(sqlite3_vtab_cursor*);
----
*xFilter*
int (*xFilter)(sqlite3_vtab_cursor*, int idxNum, const char *idxStr,
int argc, sqlite3_value **argv);
----
*xNext*
int (*xNext)(sqlite3_vtab_cursor*);
----
*xColumn*
! int (*xColumn)(sqlite3_vtab_cursor*, sqlite3_context*, int);
----
*xRowid
int (*xRowid)(sqlite3_vtab_cursor*, sqlite_int64 *pRowid);
----
*xUpdate*
! int (*xUpdate)(sqlite3_vtab *, int, sqlite3_value **, sqlite_int64 *);
--- 119,226 ----
int (*xOpen)(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor);
+ The method creates a new cursor used for reading information out
+ of a virtual table. The cursor is returned in *ppCursor.
+
+ The cursor is not immediately usable. It must first be
+ positioned using xFilter. Then elements of a row of the
+ virtual table can be accessed using xColumn and xRowid.
+
+ The xClose method is used to close the cursor.
+
----
*xClose*
int (*xClose)(sqlite3_vtab_cursor*);
+ This method closes a cursor previously opened by xOpen.
+ The SQLite core will always call xClose once for each
+ cursor opened using xOpen.
+
----
*xFilter*
int (*xFilter)(sqlite3_vtab_cursor*, int idxNum, const char *idxStr,
int argc, sqlite3_value **argv);
+ This method to begin a search of a virtual table.
+ The first argument is a cursor opened by xOpen.
+ The next two argument define a particular search
+ index previously choosen by
+ {link: wiki?p=VirtualTableBestIndexMethod xBestIndex}
+ The specific meanings of idxNum and idxStr are unimportant
+ as long as xFilter and xBestIndex agree on what that meaning
+ is.
+
+ The xBestIndex function may have requested the values
+ of certain expressions. Those values are passed in
+ using the argc and argv parameters.
+
+ After this method completes, the cursor should be left
+ pointing at a row of virtual table. The xColumn and
+ xRowid methods can be used to access that row. The
+ xNext method can be used to advance to the next row.
+
----
*xNext*
int (*xNext)(sqlite3_vtab_cursor*);
+ This method advances a virtual table cursor to the
+ next row of a result set initiated by xFilter.
+ If the cursor is already pointing at the last row
+ this routine returns 0 to indicate that no rows
+ remain. If the cursor was successfully advanced,
+ this routine returns 1.
+
----
*xColumn*
! int (*xColumn)(sqlite3_vtab_cursor*, sqlite3_context*, int N);
!
! The SQLite core invokes this method in order to find the
! value for the N-th column of the current row.
! N is zero-based so the first column is numbered 0.
! The xColumn method uses one of the sqlite3_result_AAAA()
! APIs to return the result. This method can invoke
! sqlite3_result_error() to raise an exception, if desired.
----
*xRowid
int (*xRowid)(sqlite3_vtab_cursor*, sqlite_int64 *pRowid);
+ This method writes the 64-bit rowid of the current row
+ into *pRowid.
+
----
*xUpdate*
! int (*xUpdate)(
! sqlite3_vtab *pCursor,
! int argc,
! sqlite3_value **argv,
! sqlite_int64 *pRowid
! );
!
! All changes to a virtual table are made using the xUpdate
! method. This one method can be used to insert, delete, or
! update.
!
! The argv[0] parameter is the rowid of a row in the virtual
! table to be deleted. If argv[0] is NULL, then no deletion
! occurs.
!
! The argv[1] parameter is the rowid of a new row to be
! inserted into the virtual table. Subsequence argv[]
! entries contain values of the columns of the virtual table,
! in the order that the columns were declared. The number
! of columns will match the table declaration that the
! xConnect or xCreate method made using the
! sqlite3_declare_vtab() call.
!
! If argc==1, then no insert occurs.
!
! If argc>1 and argv[0]==argv[1] then the specified row
! is updated with new values contained in argv[2] and the
! following parameters.
Small. Fast. Reliable.
Choose any three.
Choose any three.
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