opcode.html

sqlite3源码,适合作为嵌入式（embedded）

15&nbsp;&nbsp;&nbsp;&nbsp;NotExists&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;17&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
16&nbsp;&nbsp;&nbsp;&nbsp;Delete&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tbl&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
17&nbsp;&nbsp;&nbsp;&nbsp;Goto&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;14&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
18&nbsp;&nbsp;&nbsp;&nbsp;Close&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
19&nbsp;&nbsp;&nbsp;&nbsp;Halt&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
20&nbsp;&nbsp;&nbsp;&nbsp;Transaction&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
21&nbsp;&nbsp;&nbsp;&nbsp;VerifyCookie&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
22&nbsp;&nbsp;&nbsp;&nbsp;TableLock&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-1&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tbl&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
23&nbsp;&nbsp;&nbsp;&nbsp;Goto&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;00</tt></blockquote>

<p>All you have to do is add the <a href="lang_explain.html">EXPLAIN</a> keyword to the front of the
SQL statement.  But if you use the ".explain" command in the CLI,
it will set up the output mode to make the program more easily
viewable.</p>

<p>Depending on compile-time options, you 
can put the SQLite virtual machine in a mode where it will trace its
execution by writing messages to standard output.  The non-standard
SQL "PRAGMA" comments can be used to turn tracing on and off.  To
turn tracing on, enter:
</p>

<blockquote><pre>
PRAGMA vdbe_trace=on;
</pre></blockquote>

<p>
You can turn tracing back off by entering a similar statement but
changing the value "on" to "off".</p>

<h3>The Opcodes</h3>

<p>There are currently 135
opcodes defined by the virtual machine.
All currently defined opcodes are described in the table below.
This table was generated automatically by scanning the source code
from the file <b>vdbe.c</b>.</p>

<p><table cellspacing="1" border="1" cellpadding="10">
<tr><th>Opcode&nbsp;Name</th><th>Description</th></tr>

<tr><td valign="top" align="center"><a name="Add"></a><p>Add</p><td><p>Add the value in register P1 to the value in register P2
and store the result in register P3.
If either input is NULL, the result is NULL.</td></tr><tr><td valign="top" align="center"><a name="AddImm"></a><p>AddImm</p><td><p>Add the constant P2 to the value in register P1.
The result is always an integer.</p>

<p>To force any register to be an integer, just add 0.</td></tr><tr><td valign="top" align="center"><a name="Affinity"></a><p>Affinity</p><td><p>Apply affinities to a range of P2 registers starting with P1.</p>

<p>P4 is a string that is P2 characters long. The nth character of the
string indicates the column affinity that should be used for the nth
memory cell in the range.</td></tr><tr><td valign="top" align="center"><a name="AggFinal"></a><p>AggFinal</p><td><p>Execute the finalizer function for an aggregate.  P1 is
the memory location that is the accumulator for the aggregate.</p>

<p>P2 is the number of arguments that the step function takes and
P4 is a pointer to the FuncDef for this function.  The P2
argument is not used by this opcode.  It is only there to disambiguate
functions that can take varying numbers of arguments.  The
P4 argument is only needed for the degenerate case where
the step function was not previously called.</td></tr><tr><td valign="top" align="center"><a name="AggStep"></a><p>AggStep</p><td><p>Execute the step function for an aggregate.  The
function has P5 arguments.   P4 is a pointer to the FuncDef
structure that specifies the function.  Use register
P3 as the accumulator.</p>

<p>The P5 arguments are taken from register P2 and its
successors.</td></tr><tr><td valign="top" align="center"><a name="And"></a><p>And</p><td><p>Take the logical AND of the values in registers P1 and P2 and
write the result into register P3.</p>

<p>If either P1 or P2 is 0 (false) then the result is 0 even if
the other input is NULL.  A NULL and true or two NULLs give
a NULL output.</td></tr><tr><td valign="top" align="center"><a name="AutoCommit"></a><p>AutoCommit</p><td><p>Set the database auto-commit flag to P1 (1 or 0). If P2 is true, roll
back any currently active btree transactions. If there are any active
VMs (apart from this one), then the COMMIT or ROLLBACK statement fails.</p>

<p>This instruction causes the VM to halt.</td></tr><tr><td valign="top" align="center"><a name="BitAnd"></a><p>BitAnd</p><td><p>Take the bit-wise AND of the values in register P1 and P2 and
store the result in register P3.
If either input is NULL, the result is NULL.</td></tr><tr><td valign="top" align="center"><a name="BitNot"></a><p>BitNot</p><td><p>Interpret the content of register P1 as an integer.  Store the
ones-complement of the P1 value into register P2.  If P1 holds
a NULL then store a NULL in P2.</td></tr><tr><td valign="top" align="center"><a name="BitOr"></a><p>BitOr</p><td><p>Take the bit-wise OR of the values in register P1 and P2 and
store the result in register P3.
If either input is NULL, the result is NULL.</td></tr><tr><td valign="top" align="center"><a name="Blob"></a><p>Blob</p><td><p>P4 points to a blob of data P1 bytes long.  Store this
blob in register P2. This instruction is not coded directly
by the compiler. Instead, the compiler layer specifies
an OP_HexBlob opcode, with the hex string representation of
the blob as P4. This opcode is transformed to an OP_Blob
the first time it is executed.</td></tr><tr><td valign="top" align="center"><a name="Clear"></a><p>Clear</p><td><p>Delete all contents of the database table or index whose root page
in the database file is given by P1.  But, unlike Destroy, do not
remove the table or index from the database file.</p>

<p>The table being clear is in the main database file if P2==0.  If
P2==1 then the table to be clear is in the auxiliary database file
that is used to store tables create using CREATE TEMPORARY TABLE.</p>

<p>If the P3 value is non-zero, then the table refered to must be an
intkey table (an SQL table, not an index). In this case the row change
count is incremented by the number of rows in the table being cleared.
If P3 is greater than zero, then the value stored in register P3 is
also incremented by the number of rows in the table being cleared.</p>

<p>See also: Destroy</td></tr><tr><td valign="top" align="center"><a name="Close"></a><p>Close</p><td><p>Close a cursor previously opened as P1.  If P1 is not
currently open, this instruction is a no-op.</td></tr><tr><td valign="top" align="center"><a name="CollSeq"></a><p>CollSeq</p><td><p>P4 is a pointer to a CollSeq struct. If the next call to a user function
or aggregate calls sqlite3GetFuncCollSeq(), this collation sequence will
be returned. This is used by the built-in min(), max() and nullif()
functions.</p>

<p>The interface used by the implementation of the aforementioned functions
to retrieve the collation sequence set by this opcode is not available
publicly, only to user functions defined in func.c.</td></tr><tr><td valign="top" align="center"><a name="Column"></a><p>Column</p><td><p>Interpret the data that cursor P1 points to as a structure built using
the MakeRecord instruction.  (See the MakeRecord opcode for additional
information about the format of the data.)  Extract the P2-th column
from this record.  If there are less that (P2+1)
values in the record, extract a NULL.</p>

<p>The value extracted is stored in register P3.</p>

<p>If the column contains fewer than P2 fields, then extract a NULL.  Or,
if the P4 argument is a P4_MEM use the value of the P4 argument as
the result.</td></tr><tr><td valign="top" align="center"><a name="Compare"></a><p>Compare</p><td><p>Compare to vectors of registers in reg(P1)..reg(P1+P3-1) (all this
one "A") and in reg(P2)..reg(P2+P3-1) ("B").  Save the result of
the comparison for use by the next OP_Jump instruct.</p>

<p>P4 is a KeyInfo structure that defines collating sequences and sort
orders for the comparison.  The permutation applies to registers
only.  The KeyInfo elements are used sequentially.</p>

<p>The comparison is a sort comparison, so NULLs compare equal,
NULLs are less than numbers, numbers are less than strings,
and strings are less than blobs.</td></tr><tr><td valign="top" align="center"><a name="Concat"></a><p>Concat</p><td><p>Add the text in register P1 onto the end of the text in
register P2 and store the result in register P3.
If either the P1 or P2 text are NULL then store NULL in P3.</p>

<p>P3 = P2 || P1</p>

<p>It is illegal for P1 and P3 to be the same register. Sometimes,
if P3 is the same register as P2, the implementation is able
to avoid a memcpy().</td></tr><tr><td valign="top" align="center"><a name="ContextPop"></a><p>ContextPop</p><td><p>Restore the Vdbe context to the state it was in when contextPush was last
executed. The context stores the last insert row id, the last statement
change count, and the current statement change count.</td></tr><tr><td valign="top" align="center"><a name="ContextPush"></a><p>ContextPush</p><td><p>Save the current Vdbe context such that it can be restored by a ContextPop
opcode. The context stores the last insert row id, the last statement change
count, and the current statement change count.</td></tr><tr><td valign="top" align="center"><a name="Copy"></a><p>Copy</p><td><p>Make a copy of register P1 into register P2.</p>

<p>This instruction makes a deep copy of the value.  A duplicate
is made of any string or blob constant.  See also OP_SCopy.</td></tr><tr><td valign="top" align="center"><a name="CreateIndex"></a><p>CreateIndex</p><td><p>Allocate a new index in the main database file if P1==0 or in the
auxiliary database file if P1==1 or in an attached database if
P1&gt;1.  Write the root page number of the new table into
register P2.</p>

<p>See documentation on OP_CreateTable for additional information.</td></tr><tr><td valign="top" align="center"><a name="CreateTable"></a><p>CreateTable</p><td><p>Allocate a new table in the main database file if P1==0 or in the
auxiliary database file if P1==1 or in an attached database if
P1&gt;1.  Write the root page number of the new table into
register P2</p>

<p>The difference between a table and an index is this:  A table must
have a 4-byte integer key and can have arbitrary data.  An index
has an arbitrary key but no data.</p>

<p>See also: CreateIndex</td></tr><tr><td valign="top" align="center"><a name="Delete"></a><p>Delete</p><td><p>Delete the record at which the P1 cursor is currently pointing.</p>

<p>The cursor will be left pointing at either the next or the previous
record in the table. If it is left pointing at the next record, then
the next Next instruction will be a no-op.  Hence it is OK to delete
a record from within an Next loop.</p>

<p>If the OPFLAG_NCHANGE flag of P2 is set, then the row change count is
incremented (otherwise not).</p>

<p>P1 must not be pseudo-table.  It has to be a real table with
multiple rows.</p>

<p>If P4 is not NULL, then it is the name of the table that P1 is
pointing to.  The update hook will be invoked, if it exists.
If P4 is not NULL then the P1 cursor must have been positioned
using OP_NotFound prior to invoking this opcode.</td></tr><tr><td valign="top" align="center"><a name="Destroy"></a><p>Destroy</p><td><p>Delete an entire database table or index whose root page in the database
file is given by P1.</p>

<p>The table being destroyed is in the main database file if P3==0.  If
P3==1 then the table to be clear is in the auxiliary database file
that is used to store tables create using CREATE TEMPORARY TABLE.</p>

<p>If AUTOVACUUM is enabled then it is possible that another root page
might be moved into the newly deleted root page in order to keep all
root pages contiguous at the beginning of the database.  The former
value of the root page that moved - its value before the move occurred -
is stored in register P2.  If no page
movement was required (because the table being dropped was already
the last one in the database) then a zero is stored in register P2.
If AUTOVACUUM is disabled then a zero is stored in register P2.</p>