SQLite

i64 sqlite3BtreeIntegerKey(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->curIntKey );
  getCellInfo(pCur);
  return pCur->info.nKey;
}

/*
** Return the offset into the database file for the start of the
** payload to which the cursor is pointing.
*/
i64 sqlite3BtreeLocation(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->curIntKey );
  getCellInfo(pCur);
  return (i64)pCur->pBt->pageSize*(i64)pCur->pPage->pgno +
         (i64)(pCur->info.pPayload - pCur->pPage->aData);
}

/*
** Return the number of bytes of payload for the entry that pCur is
** currently pointing to.  For table btrees, this will be the amount
** of data.  For index btrees, this will be the size of the key.
**
** The caller must guarantee that the cursor is pointing to a non-NULL

                       int flags, int seekResult);
int sqlite3BtreeFirst(BtCursor*, int *pRes);
int sqlite3BtreeLast(BtCursor*, int *pRes);
int sqlite3BtreeNext(BtCursor*, int flags);
int sqlite3BtreeEof(BtCursor*);
int sqlite3BtreePrevious(BtCursor*, int flags);
i64 sqlite3BtreeIntegerKey(BtCursor*);
i64 sqlite3BtreeLocation(BtCursor*);
int sqlite3BtreePayload(BtCursor*, u32 offset, u32 amt, void*);
const void *sqlite3BtreePayloadFetch(BtCursor*, u32 *pAmt);
u32 sqlite3BtreePayloadSize(BtCursor*);

char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot, int, int*);
struct Pager *sqlite3BtreePager(Btree*);
i64 sqlite3BtreeRowCountEst(BtCursor*);

        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[0].pExpr);
      }
#endif
      if( pDef->funcFlags & SQLITE_FUNC_NEEDCOLL ){
        if( !pColl ) pColl = db->pDfltColl; 
        sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
      }
      if( pDef->funcFlags & SQLITE_FUNC_LOCATION ){
        Expr *pArg = pFarg->a[0].pExpr;
        if( pArg->op==TK_COLUMN ){
          sqlite3VdbeAddOp2(v, OP_Location, pArg->iTable, target);
        }else{
          sqlite3VdbeAddOp2(v, OP_Null, 0, target);
        }
      }else{
        sqlite3VdbeAddOp4(v, pParse->iSelfTab ? OP_PureFunc0 : OP_Function0,
                          constMask, r1, target, (char*)pDef, P4_FUNCDEF);
        sqlite3VdbeChangeP5(v, (u8)nFarg);
      }
      if( nFarg && constMask==0 ){
        sqlite3ReleaseTempRange(pParse, r1, nFarg);
      }
      return target;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_EXISTS:

#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
    FUNCTION2(unlikely,          1, 0, 0, noopFunc,  SQLITE_FUNC_UNLIKELY),
    FUNCTION2(likelihood,        2, 0, 0, noopFunc,  SQLITE_FUNC_UNLIKELY),
    FUNCTION2(likely,            1, 0, 0, noopFunc,  SQLITE_FUNC_UNLIKELY),
#ifdef SQLITE_DEBUG
    FUNCTION2(affinity,          1, 0, 0, noopFunc,  SQLITE_FUNC_AFFINITY),
#endif
    FUNCTION2(location,          1, 0, 0, noopFunc,  SQLITE_FUNC_LOCATION|
                                                     SQLITE_FUNC_TYPEOF),
    FUNCTION(ltrim,              1, 1, 0, trimFunc         ),
    FUNCTION(ltrim,              2, 1, 0, trimFunc         ),
    FUNCTION(rtrim,              1, 2, 0, trimFunc         ),
    FUNCTION(rtrim,              2, 2, 0, trimFunc         ),
    FUNCTION(trim,               1, 3, 0, trimFunc         ),
    FUNCTION(trim,               2, 3, 0, trimFunc         ),
    FUNCTION(min,               -1, 0, 1, minmaxFunc       ),

#define SQLITE_FUNC_COALESCE 0x0200 /* Built-in coalesce() or ifnull() */
#define SQLITE_FUNC_UNLIKELY 0x0400 /* Built-in unlikely() function */
#define SQLITE_FUNC_CONSTANT 0x0800 /* Constant inputs give a constant output */
#define SQLITE_FUNC_MINMAX   0x1000 /* True for min() and max() aggregates */
#define SQLITE_FUNC_SLOCHNG  0x2000 /* "Slow Change". Value constant during a
                                    ** single query - might change over time */
#define SQLITE_FUNC_AFFINITY 0x4000 /* Built-in affinity() function */
#define SQLITE_FUNC_LOCATION 0x8000 /* Built-in location() function */

/*
** The following three macros, FUNCTION(), LIKEFUNC() and AGGREGATE() are
** used to create the initializers for the FuncDef structures.
**
**   FUNCTION(zName, nArg, iArg, bNC, xFunc)
**     Used to create a scalar function definition of a function zName

  assert( p->apCsr[pOp->p1]!=0 );
  if( p->apCsr[pOp->p1]->nullRow ){
    sqlite3VdbeMemSetNull(aMem + pOp->p3);
    goto jump_to_p2;
  }
  break;
}

/* Opcode: Location P1 P2 * * *
** Synopsis: r[P2] = location(P1)
**
** Store in register r[P2] the location in the database file that is the
** start of the payload for the record at which that cursor P1 is currently
** pointing.
*/
case OP_Location: {          /* out2 */
  VdbeCursor *pC;    /* The VDBE cursor */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  pOut = out2Prerelease(p, pOp);
  if( pC==0 || pC->eCurType!=CURTYPE_BTREE ){
    pOut->flags = MEM_Null;
  }else{
    pOut->u.i = sqlite3BtreeLocation(pC->uc.pCursor);
  }
  break;
}

/* Opcode: Column P1 P2 P3 P4 P5
** Synopsis: r[P3]=PX
**
** 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

# 2017-12-16
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#*************************************************************************
#
# Test cases for the location() function.
#
set testdir [file dirname $argv0]
source $testdir/tester.tcl

do_execsql_test func6-100 {
  CREATE TABLE t1(a,b,c,d);
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100)
   INSERT INTO t1(a,b,c,d) SELECT printf('abc%03x',x), x, 1000-x, NULL FROM c;
}
do_execsql_test func6-110 {
  SELECT a, typeof(location(a)) FROM t1 ORDER BY rowid LIMIT 2;
} {abc001 integer abc002 integer}
do_execsql_test func6-120 {
  SELECT a, typeof(location(+a)) FROM t1 ORDER BY rowid LIMIT 2;
} {abc001 null abc002 null}
do_execsql_test func6-130 {
  CREATE INDEX t1a ON t1(a);
  SELECT a, typeof(location(a)) FROM t1 ORDER BY a LIMIT 2;
} {abc001 null abc002 null}
do_execsql_test func6-140 {
  SELECT a, typeof(location(a)) FROM t1 NOT INDEXED ORDER BY a LIMIT 2;
} {abc001 integer abc002 integer}

finish_test