mirror of
https://github.com/featurebasedb/featurebase.git
synced 2026-08-28 02:44:59 +00:00
c304991e9f
* implemented extract ddl; tightened up type related stuff
* added some test coverage
* review feedback
(cherry picked from commit f62313762c)
124 lines
2.6 KiB
Go
124 lines
2.6 KiB
Go
// Copyright 2022 Molecula Corp. All rights reserved.
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package planner
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import (
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"context"
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"fmt"
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"github.com/molecula/featurebase/v3/sql3"
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"github.com/molecula/featurebase/v3/sql3/planner/types"
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)
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// PlanOpTop implements the TOP operator
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type PlanOpTop struct {
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ChildOp types.PlanOperator
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expr types.PlanExpression
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warnings []string
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}
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func NewPlanOpTop(expr types.PlanExpression, child types.PlanOperator) *PlanOpTop {
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return &PlanOpTop{
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ChildOp: child,
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expr: expr,
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warnings: make([]string, 0),
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}
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}
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func (p *PlanOpTop) Schema() types.Schema {
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return p.ChildOp.Schema()
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}
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func (p *PlanOpTop) Iterator(ctx context.Context, row types.Row) (types.RowIterator, error) {
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iter, err := p.ChildOp.Iterator(ctx, row)
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if err != nil {
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return nil, err
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}
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return newTopIter(p.expr, iter), nil
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}
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func (p *PlanOpTop) Children() []types.PlanOperator {
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return []types.PlanOperator{
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p.ChildOp,
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}
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}
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func (p *PlanOpTop) WithChildren(children ...types.PlanOperator) (types.PlanOperator, error) {
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if len(children) != 1 {
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return nil, sql3.NewErrInternalf("unexpected number of children '%d'", len(children))
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}
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return NewPlanOpTop(p.expr, children[0]), nil
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}
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func (p *PlanOpTop) Plan() map[string]interface{} {
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result := make(map[string]interface{})
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result["_op"] = fmt.Sprintf("%T", p)
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sc := make([]string, 0)
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for _, e := range p.Schema() {
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sc = append(sc, fmt.Sprintf("'%s', '%s', '%s'", e.ColumnName, e.RelationName, e.Type.TypeDescription()))
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}
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result["_schema"] = sc
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result["expr"] = p.expr
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result["child"] = p.ChildOp.Plan()
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return result
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}
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func (p *PlanOpTop) String() string {
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return ""
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}
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func (p *PlanOpTop) AddWarning(warning string) {
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p.warnings = append(p.warnings, warning)
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}
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func (p *PlanOpTop) Warnings() []string {
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var w []string
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w = append(w, p.warnings...)
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w = append(w, p.ChildOp.Warnings()...)
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return w
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}
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type topIter struct {
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child types.RowIterator
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expr types.PlanExpression
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rowCount int64
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topValue int64
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hasStarted *struct{}
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}
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func newTopIter(expr types.PlanExpression, child types.RowIterator) *topIter {
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return &topIter{
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child: child,
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expr: expr,
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}
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}
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func (i *topIter) Next(ctx context.Context) (types.Row, error) {
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if i.hasStarted == nil {
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topEval, err := i.expr.Evaluate(nil)
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if err != nil {
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return nil, err
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}
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var ok bool
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i.topValue, ok = topEval.(int64)
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if !ok {
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return nil, sql3.NewErrInternalf("unexpected top expression result type %T", topEval)
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}
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i.hasStarted = &struct{}{}
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}
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if i.rowCount >= i.topValue {
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return nil, types.ErrNoMoreRows
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}
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row, err := i.child.Next(ctx)
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if err != nil {
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return nil, err
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}
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i.rowCount++
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return row, nil
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}
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