go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/analysis/internal/aip/orderby_generator.go (about)

     1  // Copyright 2022 The LUCI Authors.
     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 aip
    16  
    17  import (
    18  	"fmt"
    19  	"strings"
    20  )
    21  
    22  // MergeWithDefaultOrder merges the specified order with the given
    23  // defaultOrder. The merge occurs as follows:
    24  //   - Ordering specified in `order` takes precedence.
    25  //   - For columns not specified in the `order` that appear in `defaultOrder`,
    26  //     ordering is applied in the order they apply in defaultOrder.
    27  func MergeWithDefaultOrder(defaultOrder []OrderBy, order []OrderBy) []OrderBy {
    28  	result := make([]OrderBy, 0, len(order)+len(defaultOrder))
    29  	seenColumns := make(map[string]struct{})
    30  	for _, o := range order {
    31  		result = append(result, o)
    32  		seenColumns[o.FieldPath.String()] = struct{}{}
    33  	}
    34  	for _, o := range defaultOrder {
    35  		if _, ok := seenColumns[o.FieldPath.String()]; !ok {
    36  			result = append(result, o)
    37  		}
    38  	}
    39  	return result
    40  }
    41  
    42  // OrderByClause returns a Standard SQL Order by clause, including
    43  // "ORDER BY" and trailing new line (if an order is specified).
    44  // If no order is specified, returns "".
    45  //
    46  // The returned order clause is safe against SQL injection; only
    47  // strings appearing from Table appear in the output.
    48  func (t *Table) OrderByClause(order []OrderBy) (string, error) {
    49  	if len(order) == 0 {
    50  		return "", nil
    51  	}
    52  	seenColumns := make(map[string]struct{})
    53  	var result strings.Builder
    54  	result.WriteString("ORDER BY ")
    55  	for i, o := range order {
    56  		if i > 0 {
    57  			result.WriteString(", ")
    58  		}
    59  		column, err := t.SortableColumnByFieldPath(o.FieldPath)
    60  		if err != nil {
    61  			return "", err
    62  		}
    63  		if _, ok := seenColumns[column.databaseName]; ok {
    64  			return "", fmt.Errorf("field appears in order_by multiple times: %q", o.FieldPath.String())
    65  		}
    66  		seenColumns[column.databaseName] = struct{}{}
    67  		result.WriteString(column.databaseName)
    68  		if o.Descending {
    69  			result.WriteString(" DESC")
    70  		}
    71  	}
    72  	result.WriteString("\n")
    73  	return result.String(), nil
    74  }