github.com/dolthub/go-mysql-server@v0.18.0/sql/analyzer/resolve_ctes.go (about)

     1  // Copyright 2021 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package analyzer
    16  
    17  import (
    18  	"github.com/dolthub/go-mysql-server/sql"
    19  	"github.com/dolthub/go-mysql-server/sql/plan"
    20  	"github.com/dolthub/go-mysql-server/sql/transform"
    21  )
    22  
    23  const maxCteDepth = 5
    24  
    25  // schemaLength returns the length of a node's schema without actually accessing it. Useful when a node isn't yet
    26  // resolved, so Schema() could fail.
    27  func schemaLength(node sql.Node) int {
    28  	if node.Resolved() {
    29  		// a resolved node might have folded projections into a table scan
    30  		// and lack the distinct top-level nodes below
    31  		return len(node.Schema())
    32  	}
    33  	schemaLen := 0
    34  	transform.Inspect(node, func(node sql.Node) bool {
    35  		switch node := node.(type) {
    36  		case *plan.Project:
    37  			schemaLen = len(node.Projections)
    38  			return false
    39  		case *plan.GroupBy:
    40  			schemaLen = len(node.SelectedExprs)
    41  			return false
    42  		case *plan.Window:
    43  			schemaLen = len(node.SelectExprs)
    44  			return false
    45  		case *plan.JoinNode:
    46  			schemaLen = schemaLength(node.Left()) + schemaLength(node.Right())
    47  			return false
    48  		default:
    49  			return true
    50  		}
    51  	})
    52  	return schemaLen
    53  }