SQLite

#define JEACH_VALUE   1
#define JEACH_TYPE    2
#define JEACH_ATOM    3
#define JEACH_ID      4
#define JEACH_PARENT  5
#define JEACH_FULLKEY 6
#define JEACH_PATH    7
/* The xBestIndex method assumes that the JSON and ROOT columns are
** the last two columns in the table.  Should this ever changes, be
** sure to update the xBestIndex method. */
#define JEACH_JSON    8
#define JEACH_ROOT    9

  UNUSED_PARAM(pzErr);
  UNUSED_PARAM(argv);
  UNUSED_PARAM(argc);
  UNUSED_PARAM(pAux);

** 1 if the constraint is found, 3 if the constraint and zRoot are found,
** and 0 otherwise.
*/
static int jsonEachBestIndex(
  sqlite3_vtab *tab,
  sqlite3_index_info *pIdxInfo
){
  int i;
  int jsonIdx = -1;
  int rootIdx = -1;
  int i;                     /* Loop counter or computed array index */
  int aIdx[2];               /* Index of constraints for JSON and ROOT */
  int unusableMask = 0;      /* Mask of unusable JSON and ROOT constraints */
  int idxMask = 0;           /* Mask of usable == constraints JSON and ROOT */
  const struct sqlite3_index_constraint *pConstraint;

  /* This implementation assumes that JSON and ROOT are the last two
  ** columns in the table */
  assert( JEACH_ROOT == JEACH_JSON+1 );
  UNUSED_PARAM(tab);
  aIdx[0] = aIdx[1] = -1;
  pConstraint = pIdxInfo->aConstraint;
  for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
    int iCol;
    int iMask;
    if( pConstraint->iColumn < JEACH_JSON ) continue;
    iCol = pConstraint->iColumn - JEACH_JSON;
    assert( iCol==0 || iCol==1 );
    iMask = 1 << iCol;
    if( pConstraint->usable==0 ) continue;
    if( pConstraint->op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
    switch( pConstraint->iColumn ){
      case JEACH_JSON:   jsonIdx = i;    break;
    if( pConstraint->usable==0 ){
      unusableMask |= iMask;
    }else if( pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ ){
      aIdx[iCol] = i;
      idxMask |= iMask;
      case JEACH_ROOT:   rootIdx = i;    break;
      default:           /* no-op */     break;
    }
  }
  if( (unusableMask & ~idxMask)!=0 ){
    /* If there are any unusable constraints on JSON or ROOT, then reject
    ** this entire plan */
    return SQLITE_CONSTRAINT;
  }
  if( jsonIdx<0 ){
  if( aIdx[0]<0 ){
    /* No JSON input.  Leave estimatedCost at the huge value that it was
    ** initialized to to discourage the query planner from selecting this
    ** plan. */
    pIdxInfo->idxNum = 0;
    pIdxInfo->estimatedCost = 1e99;
  }else{
    pIdxInfo->estimatedCost = 1.0;
    i = aIdx[0];
    pIdxInfo->aConstraintUsage[jsonIdx].argvIndex = 1;
    pIdxInfo->aConstraintUsage[jsonIdx].omit = 1;
    if( rootIdx<0 ){
      pIdxInfo->idxNum = 1;
    pIdxInfo->aConstraintUsage[i].argvIndex = 1;
    pIdxInfo->aConstraintUsage[i].omit = 1;
    if( aIdx[1]<0 ){
      pIdxInfo->idxNum = 1;  /* Only JSON supplied.  Plan 1 */
    }else{
      i = aIdx[1];
      pIdxInfo->aConstraintUsage[rootIdx].argvIndex = 2;
      pIdxInfo->aConstraintUsage[rootIdx].omit = 1;
      pIdxInfo->idxNum = 3;
      pIdxInfo->aConstraintUsage[i].argvIndex = 2;
      pIdxInfo->aConstraintUsage[i].omit = 1;
      pIdxInfo->idxNum = 3;  /* Both JSON and ROOT are supplied.  Plan 3 */
    }
  }
  return SQLITE_OK;
}

/* Start a search on a new JSON string */
static int jsonEachFilter(