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Comment:Added preliminary documentation for the SAVEPOINT methods in virtual tables.
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SHA1:3dded2adf9d37c9e1c30e2c266f4e122e82360f0
User & Date: drh 2011-05-24 00:52:41
Context
2011-05-25
14:51
A tweak to the 8+3 filename documentation. Update to the change log. check-in: 6f298c user: drh tags: trunk
2011-05-24
00:52
Added preliminary documentation for the SAVEPOINT methods in virtual tables. check-in: 3dded2 user: drh tags: trunk
00:44
Restrict website search text to omit non-alphanumeric characters. check-in: 252855 user: drh tags: trunk
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Changes to pages/vtab.in.

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    int (*xSync)(sqlite3_vtab *pVTab);
    int (*xCommit)(sqlite3_vtab *pVTab);
    int (*xRollback)(sqlite3_vtab *pVTab);
    int (*xFindFunction)(sqlite3_vtab *pVtab, int nArg, const char *zName,
                       void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
                       void **ppArg);
    int (*Rename)(sqlite3_vtab *pVtab, const char *zNew);





  };
</pre></blockquote>

<p>The module structure defines all of the methods for each virtual 
table object. The module structure also contains the iVersion field which
defines the particular edition of the module table structure. Currently, 
iVersion is always 1, but in future releases of SQLite the module structure 
................................................................................

<p>This method provides notification that the virtual table implementation
that the virtual table will be given a new name. 
If this method returns [SQLITE_OK] then SQLite renames the table.
If this method returns an [error code] then the renaming is prevented.

<p>The xRename method is required for every virtual table implementation.











































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    int (*xSync)(sqlite3_vtab *pVTab);
    int (*xCommit)(sqlite3_vtab *pVTab);
    int (*xRollback)(sqlite3_vtab *pVTab);
    int (*xFindFunction)(sqlite3_vtab *pVtab, int nArg, const char *zName,
                       void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
                       void **ppArg);
    int (*Rename)(sqlite3_vtab *pVtab, const char *zNew);
    /* The methods above are in version 1 of the sqlite_module object. Those 
    ** below are for version 2 and greater. */
    int (*xSavepoint)(sqlite3_vtab *pVTab, int);
    int (*xRelease)(sqlite3_vtab *pVTab, int);
    int (*xRollbackTo)(sqlite3_vtab *pVTab, int);
  };
</pre></blockquote>

<p>The module structure defines all of the methods for each virtual 
table object. The module structure also contains the iVersion field which
defines the particular edition of the module table structure. Currently, 
iVersion is always 1, but in future releases of SQLite the module structure 
................................................................................

<p>This method provides notification that the virtual table implementation
that the virtual table will be given a new name. 
If this method returns [SQLITE_OK] then SQLite renames the table.
If this method returns an [error code] then the renaming is prevented.

<p>The xRename method is required for every virtual table implementation.

<tcl>############################################################# xSavepoint
hd_fragment xsavepoint {sqlite3_module.xSavepoint} {xSavepoint}\
  xRelease xRollbackTo</tcl>
<h3>2.20 The xSavepoint, xRelease, and xRollbackTo Methods</h3>

<blockquote><pre>
  int (*xSavepoint)(sqlite3_vtab *pVtab, int);
  int (*xRelease)(sqlite3_vtab *pVtab, int);
  int (*xRollbackTo)(sqlite3_vtab *pVtab, int);
</pre></blockquote>

<p>
These methods provide the virtual table implementation an opportunity to
implement nested transactions.  They are always optional and will only be
called in SQLite [version 3.7.7] and later.
</p>

<p>
^When xSavepoint(X,N) is invoked, that is a signal to the virtual table X
that it should save its current state as savepoint N.  
^A subsequent call
to xRollbackTo(X,R) means that the state of the virtual table should return
to what it was when xSavepoint(X,R) was last called.  
^The call
to xRollbackTo(X,R) will invalidate all savepoints with N>R; none of the
invalided savepoints will be rolled back or released without first
being reinitialized by a call to xSavepoint().  
^A call to xRelease(X,M) invalidates all savepoints where N>=M.
</p>

<p>
^None of the xSavepoint(), xRelease(), or xRollbackTo() methods will ever
be called except in between calls to xBegin() and 
either xCommit() or xRollback().
</p>