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scanner.go
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scanner.go
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package zbuf
import (
"context"
"fmt"
"sync/atomic"
"github.com/brimdata/zed"
"github.com/brimdata/zed/runtime/sam/expr"
"github.com/brimdata/zed/zio"
)
type Filter interface {
AsEvaluator() (expr.Evaluator, error)
AsBufferFilter() (*expr.BufferFilter, error)
}
// ScannerAble is implemented by Readers that provide an optimized
// implementation of the Scanner interface.
type ScannerAble interface {
NewScanner(ctx context.Context, filterExpr Filter) (Scanner, error)
}
// A Meter provides Progress statistics.
type Meter interface {
Progress() Progress
}
// A Scanner is a Batch source that also provides progress updates.
type Scanner interface {
Meter
Puller
}
// Progress represents progress statistics from a Scanner.
type Progress struct {
BytesRead int64 `zed:"bytes_read" json:"bytes_read"`
BytesMatched int64 `zed:"bytes_matched" json:"bytes_matched"`
RecordsRead int64 `zed:"records_read" json:"records_read"`
RecordsMatched int64 `zed:"records_matched" json:"records_matched"`
}
var _ Meter = (*Progress)(nil)
// Add updates its receiver by adding to it the values in ss.
func (p *Progress) Add(in Progress) {
if p != nil {
atomic.AddInt64(&p.BytesRead, in.BytesRead)
atomic.AddInt64(&p.BytesMatched, in.BytesMatched)
atomic.AddInt64(&p.RecordsRead, in.RecordsRead)
atomic.AddInt64(&p.RecordsMatched, in.RecordsMatched)
}
}
func (p *Progress) Copy() Progress {
if p == nil {
return Progress{}
}
return Progress{
BytesRead: atomic.LoadInt64(&p.BytesRead),
BytesMatched: atomic.LoadInt64(&p.BytesMatched),
RecordsRead: atomic.LoadInt64(&p.RecordsRead),
RecordsMatched: atomic.LoadInt64(&p.RecordsMatched),
}
}
func (p *Progress) Progress() Progress {
return p.Copy()
}
// NewScanner returns a Scanner for r that filters records by filterExpr and s.
// If r implements fmt.Stringer, the scanner reports errors using a prefix of the
// string returned by its String method.
func NewScanner(ctx context.Context, r zio.Reader, filterExpr Filter) (Scanner, error) {
s, err := newScanner(ctx, r, filterExpr)
if err != nil {
return nil, err
}
if stringer, ok := r.(fmt.Stringer); ok {
s = NamedScanner(s, stringer.String())
}
return s, nil
}
func newScanner(ctx context.Context, r zio.Reader, filterExpr Filter) (Scanner, error) {
var sa ScannerAble
if zf, ok := r.(*File); ok {
sa, _ = zf.Reader.(ScannerAble)
} else {
sa, _ = r.(ScannerAble)
}
if sa != nil {
return sa.NewScanner(ctx, filterExpr)
}
var f expr.Evaluator
if filterExpr != nil {
var err error
if f, err = filterExpr.AsEvaluator(); err != nil {
return nil, err
}
}
sc := &scanner{reader: r, filter: f, ctx: ctx, ectx: expr.NewContext()}
sc.Puller = NewPuller(sc)
return sc, nil
}
type scanner struct {
Puller
reader zio.Reader
filter expr.Evaluator
ctx context.Context
ectx expr.Context
progress Progress
}
func (s *scanner) Progress() Progress {
return s.progress.Copy()
}
// Read implements Reader.Read.
func (s *scanner) Read() (*zed.Value, error) {
for {
if err := s.ctx.Err(); err != nil {
return nil, err
}
this, err := s.reader.Read()
if err != nil || this == nil {
return nil, err
}
atomic.AddInt64(&s.progress.BytesRead, int64(len(this.Bytes())))
atomic.AddInt64(&s.progress.RecordsRead, 1)
if s.filter != nil {
val := s.filter.Eval(s.ectx, *this)
if !(val.Type() == zed.TypeBool && val.Bool()) {
continue
}
}
atomic.AddInt64(&s.progress.BytesMatched, int64(len(this.Bytes())))
atomic.AddInt64(&s.progress.RecordsMatched, 1)
return this, nil
}
}
type MultiStats []Scanner
func (m MultiStats) Progress() Progress {
var ss Progress
for _, s := range m {
ss.Add(s.Progress())
}
return ss
}
func NamedScanner(s Scanner, name string) *namedScanner {
return &namedScanner{
Scanner: s,
name: name,
}
}
type namedScanner struct {
Scanner
name string
}
func (n *namedScanner) Pull(done bool) (Batch, error) {
b, err := n.Scanner.Pull(done)
if err != nil {
err = fmt.Errorf("%s: %w", n.name, err)
}
return b, err
}
func MultiScanner(scanners ...Scanner) Scanner {
return &multiScanner{scanners: scanners}
}
type multiScanner struct {
scanners []Scanner
progress Progress
}
func (m *multiScanner) Pull(done bool) (Batch, error) {
for len(m.scanners) > 0 {
batch, err := m.scanners[0].Pull(done)
if batch != nil || err != nil {
return batch, err
}
m.progress.Add(m.scanners[0].Progress())
m.scanners = m.scanners[1:]
}
return nil, nil
}
func (m *multiScanner) Progress() Progress {
return m.progress.Copy()
}