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Overview
Comment:Improved comments on VDBE opcodes, for better documentation. No code or logic changes.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1:2d32e4876e0b162730f81e5c2658be12d64a9a99
User & Date: drh 2014-07-25 18:37:42
Context
2014-07-25
21:35
Try to fix harmless compiler warnings reported by Fortify. check-in: e0fa6fdc user: drh tags: trunk
18:37
Improved comments on VDBE opcodes, for better documentation. No code or logic changes. check-in: 2d32e487 user: drh tags: trunk
18:01
Add constraints (enforced only when SQLITE_DEBUG is enabled) on the use of OP_Next and OP_Prev. check-in: 2230c74f user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/vdbe.c.

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  pc = (int)pIn1->u.i;
  pIn1->flags = MEM_Undefined;
  break;
}

/* Opcode: InitCoroutine P1 P2 P3 * *
**
** Set up register P1 so that it will OP_Yield to the co-routine
** located at address P3.
**
** If P2!=0 then the co-routine implementation immediately follows
** this opcode.  So jump over the co-routine implementation to
** address P2.


*/
case OP_InitCoroutine: {     /* jump */
  assert( pOp->p1>0 &&  pOp->p1<=(p->nMem-p->nCursor) );
  assert( pOp->p2>=0 && pOp->p2<p->nOp );
  assert( pOp->p3>=0 && pOp->p3<p->nOp );
  pOut = &aMem[pOp->p1];
  assert( !VdbeMemDynamic(pOut) );
................................................................................
  pOut->flags = MEM_Int;
  if( pOp->p2 ) pc = pOp->p2 - 1;
  break;
}

/* Opcode:  EndCoroutine P1 * * * *
**
** The instruction at the address in register P1 is an OP_Yield.
** Jump to the P2 parameter of that OP_Yield.
** After the jump, register P1 becomes undefined.


*/
case OP_EndCoroutine: {           /* in1 */
  VdbeOp *pCaller;
  pIn1 = &aMem[pOp->p1];
  assert( pIn1->flags==MEM_Int );
  assert( pIn1->u.i>=0 && pIn1->u.i<p->nOp );
  pCaller = &aOp[pIn1->u.i];
................................................................................
  pc = pCaller->p2 - 1;
  pIn1->flags = MEM_Undefined;
  break;
}

/* Opcode:  Yield P1 P2 * * *
**
** Swap the program counter with the value in register P1.

**
** If the co-routine ends with OP_Yield or OP_Return then continue




** to the next instruction.  But if the co-routine ends with
** OP_EndCoroutine, jump immediately to P2.


*/
case OP_Yield: {            /* in1, jump */
  int pcDest;
  pIn1 = &aMem[pOp->p1];
  assert( VdbeMemDynamic(pIn1)==0 );
  pIn1->flags = MEM_Int;
  pcDest = (int)pIn1->u.i;
................................................................................
    sqlite3VdbeMemSetInt64(pOut, ~sqlite3VdbeIntValue(pIn1));
  }
  break;
}

/* Opcode: Once P1 P2 * * *
**
** Check if OP_Once flag P1 is set. If so, jump to instruction P2. Otherwise,
** set the flag and fall through to the next instruction.  In other words,
** this opcode causes all following opcodes up through P2 (but not including
** P2) to run just once and to be skipped on subsequent times through the loop.




*/
case OP_Once: {             /* jump */
  assert( pOp->p1<p->nOnceFlag );
  VdbeBranchTaken(p->aOnceFlag[pOp->p1]!=0, 2);
  if( p->aOnceFlag[pOp->p1] ){
    pc = pOp->p2-1;
  }else{
................................................................................
**
** Reposition cursor P1 so that  it points to the smallest entry that 
** is greater than or equal to the key value. If there are no records 
** greater than or equal to the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end.  In other words, the cursor is
** configured to use OP_Next, not OP_Prev.
**
** See also: Found, NotFound, SeekLt, SeekGt, SeekLe
*/
/* Opcode: SeekGT P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
................................................................................
**
** Reposition cursor P1 so that  it points to the smallest entry that 
** is greater than the key value. If there are no records greater than 
** the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end.  In other words, the cursor is
** configured to use OP_Next, not OP_Prev.
**
** See also: Found, NotFound, SeekLt, SeekGe, SeekLe
*/
/* Opcode: SeekLT P1 P2 P3 P4 * 
** Synopsis: key=r[P3@P4]
**
** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
................................................................................
**
** Reposition cursor P1 so that  it points to the largest entry that 
** is less than the key value. If there are no records less than 
** the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning.  In other words, the cursor is
** configured to use OP_Prev, not OP_Next.
**
** See also: Found, NotFound, SeekGt, SeekGe, SeekLe
*/
/* Opcode: SeekLE P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
................................................................................
**
** Reposition cursor P1 so that it points to the largest entry that 
** is less than or equal to the key value. If there are no records 
** less than or equal to the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning.  In other words, the cursor is
** configured to use OP_Prev, not OP_Next.
**
** See also: Found, NotFound, SeekGt, SeekGe, SeekLt
*/
case OP_SeekLT:         /* jump, in3 */
case OP_SeekLE:         /* jump, in3 */
case OP_SeekGE:         /* jump, in3 */
case OP_SeekGT: {       /* jump, in3 */
................................................................................
** will refer to the last entry in the database table or index.
** If the table or index is empty and P2>0, then jump immediately to P2.
** If P2 is 0 or if the table or index is not empty, fall through
** to the following instruction.
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning.  In other words, the cursor is
** configured to use OP_Prev, not OP_Next.
*/
case OP_Last: {        /* jump */
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
................................................................................
** will refer to the first entry in the database table or index.
** If the table or index is empty and P2>0, then jump immediately to P2.
** If P2 is 0 or if the table or index is not empty, fall through
** to the following instruction.
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end.  In other words, the cursor is
** configured to use OP_Next, not OP_Prev.
*/
case OP_Rewind: {        /* jump */
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
................................................................................
/* Opcode: Next P1 P2 P3 P4 P5
**
** Advance cursor P1 so that it points to the next key/data pair in its
** table or index.  If there are no more key/value pairs then fall through
** to the following instruction.  But if the cursor advance was successful,
** jump immediately to P2.
**
** The OP_Next opcode is only valid following an OP_SeekGT, OP_SeekGE, or
** OP_Rewind opcode used to position the cursor.  OP_Next is not allowed
** to follow OP_SeekLT, OP_SeekLE, or OP_Last.
**
** The P1 cursor must be for a real table, not a pseudo-table.  P1 must have
** been opened prior to this opcode or the program will segfault.
**
** The P3 value is a hint to the btree implementation. If P3==1, that
** means P1 is an SQL index and that this instruction could have been
** omitted if that index had been unique.  P3 is usually 0.  P3 is
................................................................................
** If P5 is positive and the jump is taken, then event counter
** number P5-1 in the prepared statement is incremented.
**
** See also: Prev, NextIfOpen
*/
/* Opcode: NextIfOpen P1 P2 P3 P4 P5
**
** This opcode works just like OP_Next except that if cursor P1 is not
** open it behaves a no-op.
*/
/* Opcode: Prev P1 P2 P3 P4 P5
**
** Back up cursor P1 so that it points to the previous key/data pair in its
** table or index.  If there is no previous key/value pairs then fall through
** to the following instruction.  But if the cursor backup was successful,
** jump immediately to P2.
**
**
** The OP_Prev opcode is only valid following an OP_SeekLT, OP_SeekLE, or
** OP_Last opcode used to position the cursor.  OP_Prev is not allowed
** to follow OP_SeekGT, OP_SeekGE, or OP_Rewind.
**
** The P1 cursor must be for a real table, not a pseudo-table.  If P1 is
** not open then the behavior is undefined.
**
** The P3 value is a hint to the btree implementation. If P3==1, that
** means P1 is an SQL index and that this instruction could have been
** omitted if that index had been unique.  P3 is usually 0.  P3 is
................................................................................
** sqlite3BtreePrevious().
**
** If P5 is positive and the jump is taken, then event counter
** number P5-1 in the prepared statement is incremented.
*/
/* Opcode: PrevIfOpen P1 P2 P3 P4 P5
**
** This opcode works just like OP_Prev except that if cursor P1 is not
** open it behaves a no-op.
*/
case OP_SorterNext: {  /* jump */
  VdbeCursor *pC;
  int res;

  pC = p->apCsr[pOp->p1];
................................................................................
}
#endif /* !defined(SQLITE_OMIT_ANALYZE) */

/* Opcode: DropTable P1 * * P4 *
**
** Remove the internal (in-memory) data structures that describe
** the table named P4 in database P1.  This is called after a table

** is dropped in order to keep the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropTable: {
  sqlite3UnlinkAndDeleteTable(db, pOp->p1, pOp->p4.z);
  break;
}

/* Opcode: DropIndex P1 * * P4 *
**
** Remove the internal (in-memory) data structures that describe
** the index named P4 in database P1.  This is called after an index

** is dropped in order to keep the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropIndex: {
  sqlite3UnlinkAndDeleteIndex(db, pOp->p1, pOp->p4.z);
  break;
}

/* Opcode: DropTrigger P1 * * P4 *
**
** Remove the internal (in-memory) data structures that describe
** the trigger named P4 in database P1.  This is called after a trigger

** is dropped in order to keep the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropTrigger: {
  sqlite3UnlinkAndDeleteTrigger(db, pOp->p1, pOp->p4.z);
  break;
}








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  pc = (int)pIn1->u.i;
  pIn1->flags = MEM_Undefined;
  break;
}

/* Opcode: InitCoroutine P1 P2 P3 * *
**
** Set up register P1 so that it will Yield to the coroutine
** located at address P3.
**
** If P2!=0 then the coroutine implementation immediately follows
** this opcode.  So jump over the coroutine implementation to
** address P2.
**
** See also: EndCoroutine
*/
case OP_InitCoroutine: {     /* jump */
  assert( pOp->p1>0 &&  pOp->p1<=(p->nMem-p->nCursor) );
  assert( pOp->p2>=0 && pOp->p2<p->nOp );
  assert( pOp->p3>=0 && pOp->p3<p->nOp );
  pOut = &aMem[pOp->p1];
  assert( !VdbeMemDynamic(pOut) );
................................................................................
  pOut->flags = MEM_Int;
  if( pOp->p2 ) pc = pOp->p2 - 1;
  break;
}

/* Opcode:  EndCoroutine P1 * * * *
**
** The instruction at the address in register P1 is an Yield.
** Jump to the P2 parameter of that Yield.
** After the jump, register P1 becomes undefined.
**
** See also: InitCoroutine
*/
case OP_EndCoroutine: {           /* in1 */
  VdbeOp *pCaller;
  pIn1 = &aMem[pOp->p1];
  assert( pIn1->flags==MEM_Int );
  assert( pIn1->u.i>=0 && pIn1->u.i<p->nOp );
  pCaller = &aOp[pIn1->u.i];
................................................................................
  pc = pCaller->p2 - 1;
  pIn1->flags = MEM_Undefined;
  break;
}

/* Opcode:  Yield P1 P2 * * *
**
** Swap the program counter with the value in register P1.  This
** has the effect of yielding to a coroutine.
**

** If the coroutine that is launched by this instruction ends with
** Yield or Return then continue to the next instruction.  But if
** the coroutine launched by this instruction ends with
** EndCoroutine, then jump to P2 rather than continuing with the
** next instruction.

**
** See also: InitCoroutine
*/
case OP_Yield: {            /* in1, jump */
  int pcDest;
  pIn1 = &aMem[pOp->p1];
  assert( VdbeMemDynamic(pIn1)==0 );
  pIn1->flags = MEM_Int;
  pcDest = (int)pIn1->u.i;
................................................................................
    sqlite3VdbeMemSetInt64(pOut, ~sqlite3VdbeIntValue(pIn1));
  }
  break;
}

/* Opcode: Once P1 P2 * * *
**
** Check the "once" flag number P1. If it is set, jump to instruction P2. 
** Otherwise, set the flag and fall through to the next instruction.
** In other words, this opcode causes all following opcodes up through P2
** (but not including P2) to run just once and to be skipped on subsequent
** times through the loop.
**
** All "once" flags are initially cleared whenever a prepared statement
** first begins to run.
*/
case OP_Once: {             /* jump */
  assert( pOp->p1<p->nOnceFlag );
  VdbeBranchTaken(p->aOnceFlag[pOp->p1]!=0, 2);
  if( p->aOnceFlag[pOp->p1] ){
    pc = pOp->p2-1;
  }else{
................................................................................
**
** Reposition cursor P1 so that  it points to the smallest entry that 
** is greater than or equal to the key value. If there are no records 
** greater than or equal to the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end.  In other words, the cursor is
** configured to use Next, not Prev.
**
** See also: Found, NotFound, SeekLt, SeekGt, SeekLe
*/
/* Opcode: SeekGT P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
................................................................................
**
** Reposition cursor P1 so that  it points to the smallest entry that 
** is greater than the key value. If there are no records greater than 
** the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end.  In other words, the cursor is
** configured to use Next, not Prev.
**
** See also: Found, NotFound, SeekLt, SeekGe, SeekLe
*/
/* Opcode: SeekLT P1 P2 P3 P4 * 
** Synopsis: key=r[P3@P4]
**
** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
................................................................................
**
** Reposition cursor P1 so that  it points to the largest entry that 
** is less than the key value. If there are no records less than 
** the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning.  In other words, the cursor is
** configured to use Prev, not Next.
**
** See also: Found, NotFound, SeekGt, SeekGe, SeekLe
*/
/* Opcode: SeekLE P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
................................................................................
**
** Reposition cursor P1 so that it points to the largest entry that 
** is less than or equal to the key value. If there are no records 
** less than or equal to the key and P2 is not zero, then jump to P2.
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning.  In other words, the cursor is
** configured to use Prev, not Next.
**
** See also: Found, NotFound, SeekGt, SeekGe, SeekLt
*/
case OP_SeekLT:         /* jump, in3 */
case OP_SeekLE:         /* jump, in3 */
case OP_SeekGE:         /* jump, in3 */
case OP_SeekGT: {       /* jump, in3 */
................................................................................
** will refer to the last entry in the database table or index.
** If the table or index is empty and P2>0, then jump immediately to P2.
** If P2 is 0 or if the table or index is not empty, fall through
** to the following instruction.
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning.  In other words, the cursor is
** configured to use Prev, not Next.
*/
case OP_Last: {        /* jump */
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
................................................................................
** will refer to the first entry in the database table or index.
** If the table or index is empty and P2>0, then jump immediately to P2.
** If P2 is 0 or if the table or index is not empty, fall through
** to the following instruction.
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end.  In other words, the cursor is
** configured to use Next, not Prev.
*/
case OP_Rewind: {        /* jump */
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
................................................................................
/* Opcode: Next P1 P2 P3 P4 P5
**
** Advance cursor P1 so that it points to the next key/data pair in its
** table or index.  If there are no more key/value pairs then fall through
** to the following instruction.  But if the cursor advance was successful,
** jump immediately to P2.
**
** The Next opcode is only valid following an SeekGT, SeekGE, or
** OP_Rewind opcode used to position the cursor.  Next is not allowed
** to follow SeekLT, SeekLE, or OP_Last.
**
** The P1 cursor must be for a real table, not a pseudo-table.  P1 must have
** been opened prior to this opcode or the program will segfault.
**
** The P3 value is a hint to the btree implementation. If P3==1, that
** means P1 is an SQL index and that this instruction could have been
** omitted if that index had been unique.  P3 is usually 0.  P3 is
................................................................................
** If P5 is positive and the jump is taken, then event counter
** number P5-1 in the prepared statement is incremented.
**
** See also: Prev, NextIfOpen
*/
/* Opcode: NextIfOpen P1 P2 P3 P4 P5
**
** This opcode works just like Next except that if cursor P1 is not
** open it behaves a no-op.
*/
/* Opcode: Prev P1 P2 P3 P4 P5
**
** Back up cursor P1 so that it points to the previous key/data pair in its
** table or index.  If there is no previous key/value pairs then fall through
** to the following instruction.  But if the cursor backup was successful,
** jump immediately to P2.
**
**
** The Prev opcode is only valid following an SeekLT, SeekLE, or
** OP_Last opcode used to position the cursor.  Prev is not allowed
** to follow SeekGT, SeekGE, or OP_Rewind.
**
** The P1 cursor must be for a real table, not a pseudo-table.  If P1 is
** not open then the behavior is undefined.
**
** The P3 value is a hint to the btree implementation. If P3==1, that
** means P1 is an SQL index and that this instruction could have been
** omitted if that index had been unique.  P3 is usually 0.  P3 is
................................................................................
** sqlite3BtreePrevious().
**
** If P5 is positive and the jump is taken, then event counter
** number P5-1 in the prepared statement is incremented.
*/
/* Opcode: PrevIfOpen P1 P2 P3 P4 P5
**
** This opcode works just like Prev except that if cursor P1 is not
** open it behaves a no-op.
*/
case OP_SorterNext: {  /* jump */
  VdbeCursor *pC;
  int res;

  pC = p->apCsr[pOp->p1];
................................................................................
}
#endif /* !defined(SQLITE_OMIT_ANALYZE) */

/* Opcode: DropTable P1 * * P4 *
**
** Remove the internal (in-memory) data structures that describe
** the table named P4 in database P1.  This is called after a table
** is dropped from disk (using the Destroy opcode) in order to keep 
** the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropTable: {
  sqlite3UnlinkAndDeleteTable(db, pOp->p1, pOp->p4.z);
  break;
}

/* Opcode: DropIndex P1 * * P4 *
**
** Remove the internal (in-memory) data structures that describe
** the index named P4 in database P1.  This is called after an index
** is dropped from disk (using the Destroy opcode)
** in order to keep the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropIndex: {
  sqlite3UnlinkAndDeleteIndex(db, pOp->p1, pOp->p4.z);
  break;
}

/* Opcode: DropTrigger P1 * * P4 *
**
** Remove the internal (in-memory) data structures that describe
** the trigger named P4 in database P1.  This is called after a trigger
** is dropped from disk (using the Destroy opcode) in order to keep 
** the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropTrigger: {
  sqlite3UnlinkAndDeleteTrigger(db, pOp->p1, pOp->p4.z);
  break;
}