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closuretab.go
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closuretab.go
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package closuretab
import (
"context"
"database/sql"
"fmt"
"strings"
)
type AttrType int
const (
Child AttrType = iota
Parent
Depth
)
type AttrMapping = map[AttrType]string
type Querier interface {
QueryRowContext(ctx context.Context, query string, args ...interface{}) *sql.Row
QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error)
}
type Node struct {
ID int64
ParentID int64
Depth int
}
type ClosureRelation struct {
table string
attrs map[AttrType]string
}
func InitClosureRelation(tableName string, attrs AttrMapping) *ClosureRelation {
return &ClosureRelation{table: tableName, attrs: attrs}
}
func (r *ClosureRelation) GetChildren(ctx context.Context, q Querier, parentID int64) ([]Node, error) {
rows, err := q.QueryContext(
ctx,
fmt.Sprintf(
"SELECT %s, %s, %s FROM %s WHERE %s = ? ORDER BY %s ASC",
r.attrs[Child], r.attrs[Parent], r.attrs[Depth], r.table,
r.attrs[Parent], r.attrs[Depth],
),
parentID,
)
if err != nil {
return nil, fmt.Errorf("get child nodes for parent ID %d: %w", parentID, err)
}
return scanNodes(rows)
}
func (r *ClosureRelation) GetParents(ctx context.Context, q Querier, nodeID int64) ([]Node, error) {
rows, err := q.QueryContext(
ctx,
fmt.Sprintf(
"SELECT %s, %s, %s FROM %s WHERE %s = ? AND %s != ? ORDER BY %s DESC",
r.attrs[Parent], r.attrs[Parent], r.attrs[Depth], r.table,
r.attrs[Child], r.attrs[Parent],
r.attrs[Depth],
),
nodeID, nodeID,
)
if err != nil {
return nil, fmt.Errorf("get parent nodes for node ID %d: %w", nodeID, err)
}
return scanNodes(rows)
}
func (r *ClosureRelation) Insert(ctx context.Context, q Querier, parentID, nodeID int64) (Node, error) {
_, err := q.ExecContext(
ctx,
fmt.Sprintf(
"INSERT INTO %s (%s, %s, %s) "+
"SELECT ?, %s, %s + 1 FROM %s WHERE %s = ?",
r.table, r.attrs[Child], r.attrs[Parent], r.attrs[Depth],
r.attrs[Parent], r.attrs[Depth], r.table, r.attrs[Child],
),
nodeID, parentID,
)
if err != nil {
return Node{}, fmt.Errorf("insert hierarchy references: %w", err)
}
_, err = q.ExecContext(
ctx,
fmt.Sprintf(
"INSERT INTO %s (%s, %s, %s) VALUES (?, ?, ?)",
r.table, r.attrs[Child], r.attrs[Parent], r.attrs[Depth],
),
nodeID, nodeID, 0,
)
if err != nil {
return Node{}, fmt.Errorf("insert self-reference: %w", err)
}
return Node{}, nil
}
func (r *ClosureRelation) Delete(ctx context.Context, q Querier, nodeID int64) error {
if _, err := q.ExecContext(
ctx,
fmt.Sprintf(
"DELETE FROM %s WHERE %s IN (SELECT %s FROM %s WHERE %s = ?)",
r.table, r.attrs[Child], r.attrs[Child], r.table, r.attrs[Parent],
),
nodeID,
); err != nil {
return fmt.Errorf("remove node ID %d: %w", nodeID, err)
}
if _, err := q.ExecContext(
ctx,
fmt.Sprintf(
"DELETE FROM %s WHERE %s = ? OR %s = ?",
r.table, r.attrs[Child], r.attrs[Parent],
),
nodeID, nodeID,
); err != nil {
return fmt.Errorf("remove node ID %d: %w", nodeID, err)
}
return nil
}
func (r *ClosureRelation) Move(ctx context.Context, q Querier, nodeID, newParentID int64) error {
if _, deleteErr := q.ExecContext(
ctx,
fmt.Sprintf(
"DELETE FROM %s "+
"WHERE %s IN "+
"(SELECT %s FROM %s WHERE %s = ?) "+
"AND %s IN "+
"(SELECT %s FROM %s WHERE %s = ? AND %s != %s) ",
r.table,
r.attrs[Child],
r.attrs[Child], r.table, r.attrs[Parent],
r.attrs[Parent],
r.attrs[Parent], r.table, r.attrs[Child], r.attrs[Parent], r.attrs[Child],
),
nodeID, nodeID,
); deleteErr != nil {
return fmt.Errorf("remove node ID %d: %w", nodeID, deleteErr)
}
parents, err := r.GetParents(ctx, q, newParentID)
if err != nil {
return fmt.Errorf("get new parents for moved nodes: %w", err)
}
parentIDs := NodeIDs(parents)
parentIDs = append(parentIDs, newParentID)
parentIDsPlaceholders := makePlaceholders("?", len(parentIDs))
children, err := r.GetChildren(ctx, q, nodeID)
if err != nil {
return fmt.Errorf("get all nodes being moved: %w", err)
}
childrenIDs := NodeIDs(children)
childrenIDsPlaceholders := makePlaceholders("?", len(childrenIDs))
args := make([]interface{}, len(parentIDs)+len(childrenIDs))
for i := 0; i < len(args); i++ {
if i < len(parentIDs) {
args[i] = parentIDs[i]
} else {
args[i] = childrenIDs[i-len(parentIDs)]
}
}
query := fmt.Sprintf(
`INSERT INTO %s (%s, %s, %s)
SELECT supertree.%s, subtree.%s, MAX(supertree.%s + subtree.%s + 1)
FROM %s AS supertree, %s AS subtree
WHERE
supertree.%s IN %s
AND subtree.%s IN %s
GROUP BY supertree.%s, subtree.%s`,
r.table, r.attrs[Parent], r.attrs[Child], r.attrs[Depth],
r.attrs[Parent], r.attrs[Child], r.attrs[Depth], r.attrs[Depth],
r.table, r.table,
r.attrs[Parent], parentIDsPlaceholders,
r.attrs[Child], childrenIDsPlaceholders,
r.attrs[Parent], r.attrs[Child],
)
if _, insertErr := q.ExecContext(
ctx,
query,
args...,
); insertErr != nil {
return fmt.Errorf("insert nodes under new parent: %w", insertErr)
}
return nil
}
func (r *ClosureRelation) Empty(ctx context.Context, q Querier) (bool, error) {
row := q.QueryRowContext(ctx, fmt.Sprintf("SELECT count(*) FROM %s", r.table))
var cnt int
if err := row.Scan(&cnt); err != nil {
return false, fmt.Errorf("count closure table rows: %w", err)
}
return cnt == 0, nil
}
func NodeIDs(nodes []Node) []int64 {
res := make([]int64, 0, len(nodes))
for i := range nodes {
res = append(res, nodes[i].ID)
}
return res
}
type scanner interface {
Scan(dest ...interface{}) error
}
func scanNodes(rows *sql.Rows) ([]Node, error) {
result := make([]Node, 0)
if _, scanErr := scanEachRow(rows, func(s scanner) error {
n := Node{}
if rowErr := s.Scan(&n.ID, &n.ParentID, &n.Depth); rowErr != nil {
return rowErr
}
result = append(result, n)
return nil
}); scanErr != nil {
return nil, fmt.Errorf("scan nodes: %w", scanErr)
}
return result, nil
}
func scanEachRow(rows *sql.Rows, scanRow func(s scanner) error) (rowsProcessed int, err error) {
defer func() { _ = rows.Close() }()
count := 0
for rows.Next() {
err = scanRow(rows)
if err != nil {
return 0, fmt.Errorf("scan row: %w", err)
}
count++
}
if err = rows.Err(); err != nil {
if err == sql.ErrNoRows {
return 0, nil
}
return 0, fmt.Errorf("rows scan: %w", err)
}
return count, nil
}
func makePlaceholders(pHolder string, argLen int) string {
pHolders := make([]string, argLen)
for i := 0; i < argLen; i++ {
pHolders[i] = pHolder
}
return fmt.Sprintf("(%s)", strings.Join(pHolders, ", "))
}