// nextRow processes table rows until it finds a row that passes the filter.
// Returns a nil row when there are no more rows.
func (tr *tableReader) nextRow() (sqlbase.EncDatumRow, error) {
for {
fetcherRow, err := tr.fetcher.NextRow()
if err != nil || fetcherRow == nil {
return nil, err
}
// TODO(radu): we are defeating the purpose of EncDatum here - we
// should modify RowFetcher to return EncDatums directly and avoid
// the cost of decoding/reencoding.
for i := range fetcherRow {
if fetcherRow[i] != nil {
tr.row[i].SetDatum(tr.desc.Columns[i].Type.Kind, fetcherRow[i])
}
}
passesFilter, err := sqlbase.RunFilter(tr.filter, tr.evalCtx)
if err != nil {
return nil, err
}
if passesFilter {
break
}
}
// TODO(radu): investigate removing this allocation. We can't reuse the
// same slice because it is being read asynchronously on the other side
// of the channel. Perhaps streamMsg can store a few preallocated
// elements to avoid allocation in most cases.
outRow := make(sqlbase.EncDatumRow, len(tr.outputCols))
for i, col := range tr.outputCols {
outRow[i] = tr.row[col]
}
return outRow, nil
}
func (n *scanNode) Next() (bool, error) {
tracing.AnnotateTrace()
if !n.scanInitialized {
if err := n.initScan(); err != nil {
return false, nil
}
}
if n.explain == explainDebug {
return n.debugNext()
}
// We fetch one row at a time until we find one that passes the filter.
for {
var err error
n.row, err = n.fetcher.NextRow()
if err != nil || n.row == nil {
return false, err
}
passesFilter, err := sqlbase.RunFilter(n.filter, n.p.evalCtx)
if err != nil {
return false, err
}
if passesFilter {
return true, nil
}
}
}
// debugNext is a helper function used by Next() when in explainDebug mode.
func (n *scanNode) debugNext() (bool, error) {
// In debug mode, we output a set of debug values for each key.
n.debugVals.rowIdx = n.rowIndex
var err error
n.debugVals.key, n.debugVals.value, n.row, err = n.fetcher.NextKeyDebug()
if err != nil || n.debugVals.key == "" {
return false, err
}
if n.row != nil {
passesFilter, err := sqlbase.RunFilter(n.filter, n.p.evalCtx)
if err != nil {
return false, err
}
if passesFilter {
n.debugVals.output = debugValueRow
} else {
n.debugVals.output = debugValueFiltered
}
n.rowIndex++
} else {
n.debugVals.output = debugValuePartial
}
return true, nil
}
func (s *selectNode) Next() (bool, error) {
for {
if next, err := s.source.plan.Next(); !next {
return false, err
}
if s.explain == explainDebug {
s.debugVals = s.source.plan.DebugValues()
if s.debugVals.output != debugValueRow {
// Let the debug values pass through.
return true, nil
}
}
row := s.source.plan.Values()
s.qvals.populateQVals(&s.source.info, row)
passesFilter, err := sqlbase.RunFilter(s.filter, &s.planner.evalCtx)
if err != nil {
return false, err
}
if passesFilter {
err := s.renderRow()
return err == nil, err
} else if s.explain == explainDebug {
// Mark the row as filtered out.
s.debugVals.output = debugValueFiltered
return true, nil
}
// Row was filtered out; grab the next row.
}
}
// evalFilter is used for filter expressions; it evaluates the expression and
// returns whether the filter passes.
func (eh *exprHelper) evalFilter(row sqlbase.EncDatumRow) (bool, error) {
eh.row = row
return sqlbase.RunFilter(eh.expr, eh.evalCtx)
}