github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/pkg/sql/subquery.go (about)

     1  // Copyright 2015 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  package sql
    12  
    13  import (
    14  	"github.com/cockroachdb/cockroach/pkg/sql/rowexec"
    15  	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
    16  	"github.com/cockroachdb/errors"
    17  )
    18  
    19  // subquery represents a subquery expression in an expression tree
    20  // after it has been converted to a query plan. It is stored in
    21  // planTop.subqueryPlans.
    22  type subquery struct {
    23  	// subquery is used to show the subquery SQL when explaining plans.
    24  	subquery tree.NodeFormatter
    25  	execMode rowexec.SubqueryExecMode
    26  	expanded bool
    27  	started  bool
    28  	plan     planMaybePhysical
    29  	result   tree.Datum
    30  }
    31  
    32  // EvalSubquery is called by `tree.Eval()` method implementations to
    33  // retrieve the Datum result of a subquery.
    34  func (p *planner) EvalSubquery(expr *tree.Subquery) (result tree.Datum, err error) {
    35  	if expr.Idx == 0 {
    36  		return nil, errors.AssertionFailedf("subquery %q was not processed", expr)
    37  	}
    38  	if expr.Idx < 0 || expr.Idx-1 >= len(p.curPlan.subqueryPlans) {
    39  		return nil, errors.AssertionFailedf("invalid index %d for %q", expr.Idx, expr)
    40  	}
    41  
    42  	s := &p.curPlan.subqueryPlans[expr.Idx-1]
    43  	if !s.started {
    44  		return nil, errors.AssertionFailedf("subquery %d (%q) not started prior to evaluation", expr.Idx, expr)
    45  	}
    46  	return s.result, nil
    47  }