Планировщик запросов. Планы #45

.golangci.yml

@@ -69,3 +69,4 @@ linters-settings:
       - Constant
       - Term
       - Statement$
+      - Scan

pkg/planner/errors.go

@@ -0,0 +1,5 @@
+package planner
+
+import "github.com/pkg/errors"
+
+var ErrFailedToCreatePlan = errors.New("failed to create plan")

pkg/planner/plan.go

@@ -0,0 +1,15 @@
+package planner
+
+import (
+	"github.com/unhandled-exception/sophiadb/pkg/records"
+	"github.com/unhandled-exception/sophiadb/pkg/scan"
+)
+
+type Plan interface {
+	Open() (scan.Scan, error)
+	Schema() records.Schema
+	BlocksAccessed() int64
+	Records() int64
+	DistinctValues(string) (int64, bool)
+	String() string
+}

pkg/planner/table_plan.go

@@ -0,0 +1,67 @@
+package planner
+
+import (
+	"fmt"
+
+	"github.com/pkg/errors"
+	"github.com/unhandled-exception/sophiadb/pkg/metadata"
+	"github.com/unhandled-exception/sophiadb/pkg/records"
+	"github.com/unhandled-exception/sophiadb/pkg/scan"
+)
+
+type TablePlan struct {
+	trx       scan.TRXInt
+	tablename string
+	layout    records.Layout
+	stats     metadata.StatInfo
+}
+
+type tablePlanMetadataManager interface {
+	Layout(tableName string, trx scan.TRXInt) (records.Layout, error)
+	GetStatInfo(tableName string, layout records.Layout, trx scan.TRXInt) (metadata.StatInfo, error)
+}
+
+func NewTablePlan(trx scan.TRXInt, tableName string, md tablePlanMetadataManager) (*TablePlan, error) {
+	p := &TablePlan{
+		trx:       trx,
+		tablename: tableName,
+	}
+
+	var err error
+
+	p.layout, err = md.Layout(tableName, trx)
+	if err != nil {
+		return nil, errors.WithMessage(ErrFailedToCreatePlan, err.Error())
+	}
+
+	p.stats, err = md.GetStatInfo(tableName, p.layout, trx)
+	if err != nil {
+		return nil, errors.WithMessage(ErrFailedToCreatePlan, err.Error())
+	}
+
+	return p, nil
+}
+
+func (p *TablePlan) Open() (scan.Scan, error) {
+	return scan.NewTableScan(p.trx, p.tablename, p.layout)
+}
+
+func (p *TablePlan) Schema() records.Schema {
+	return p.layout.Schema
+}
+
+func (p *TablePlan) BlocksAccessed() int64 {
+	return p.stats.Blocks
+}
+
+func (p *TablePlan) Records() int64 {
+	return p.stats.Records
+}
+
+func (p *TablePlan) DistinctValues(fieldName string) (int64, bool) {
+	return p.stats.DistinctValues(fieldName)
+}
+
+func (p *TablePlan) String() string {
+	return fmt.Sprintf("scan table %s", p.tablename)
+}