SimpleCloudNotifier/scnserver/db/dbtools/preprocessor.go

253 lines
6.0 KiB
Go
Raw Normal View History

package dbtools
import (
"context"
"errors"
"fmt"
"github.com/rs/zerolog/log"
"gogs.mikescher.com/BlackForestBytes/goext/langext"
2023-01-15 06:30:30 +01:00
"gogs.mikescher.com/BlackForestBytes/goext/rext"
"gogs.mikescher.com/BlackForestBytes/goext/sq"
"regexp"
"strings"
"sync"
"time"
)
//
// This is..., not good...
//
// for sq.ScanAll to work with (left-)joined tables _need_ to get column names aka "alias.column"
// But sqlite (and all other db server) only return "column" if we don't manually specify `alias.column as "alias.columnname"`
// But always specifying all columns (and their alias) would be __very__ cumbersome...
//
// The "solution" is this preprocessor, which translates queries of the form `SELECT tab1.*, tab2.* From tab1` into `SELECT tab1.col1 AS "tab1.col1", tab1.col2 AS "tab1.col2" ....`
//
// Prerequisites:
// - all aliased tables must be written as `tablename AS alias` (the variant without the AS keyword is invalid)
// - a star only expands to the (single) table in FROM. Use *, table2.* if there exists a second (joined) table
// - No weird SQL syntax, this "parser" is not very robust...
//
type DBPreprocessor struct {
db sq.DB
lock sync.Mutex
dbTables []string
dbColumns map[string][]string
cacheQuery map[string]string
}
2023-01-15 06:30:30 +01:00
var regexAlias = rext.W(regexp.MustCompile("([A-Za-z_\\-0-9]+)\\s+AS\\s+([A-Za-z_\\-0-9]+)"))
func NewDBPreprocessor(db sq.DB) (*DBPreprocessor, error) {
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
obj := &DBPreprocessor{
db: db,
lock: sync.Mutex{},
cacheQuery: make(map[string]string),
}
err := obj.Init(ctx)
if err != nil {
return nil, err
}
return obj, nil
}
func (pp *DBPreprocessor) Init(ctx context.Context) error {
dbTables := make([]string, 0)
dbColumns := make(map[string][]string, 0)
type tabInfo struct {
Name string `db:"name"`
}
type colInfo struct {
Name string `db:"name"`
}
rows1, err := pp.db.Query(ctx, "PRAGMA table_list;", sq.PP{})
if err != nil {
return err
}
resrows1, err := sq.ScanAll[tabInfo](rows1, sq.SModeFast, sq.Unsafe, true)
if err != nil {
return err
}
for _, tab := range resrows1 {
rows2, err := pp.db.Query(ctx, fmt.Sprintf("PRAGMA table_info(\"%s\");", tab.Name), sq.PP{})
if err != nil {
return err
}
resrows2, err := sq.ScanAll[colInfo](rows2, sq.SModeFast, sq.Unsafe, true)
if err != nil {
return err
}
columns := langext.ArrMap(resrows2, func(v colInfo) string { return v.Name })
dbTables = append(dbTables, tab.Name)
dbColumns[tab.Name] = columns
}
pp.dbTables = dbTables
pp.dbColumns = dbColumns
return nil
}
func (pp *DBPreprocessor) PrePing(ctx context.Context) error {
return nil
}
func (pp *DBPreprocessor) PreTxBegin(ctx context.Context, txid uint16) error {
return nil
}
func (pp *DBPreprocessor) PreTxCommit(txid uint16) error {
return nil
}
func (pp *DBPreprocessor) PreTxRollback(txid uint16) error {
return nil
}
func (pp *DBPreprocessor) PreQuery(ctx context.Context, txID *uint16, sql *string, params *sq.PP) error {
sqlOriginal := *sql
pp.lock.Lock()
v, ok := pp.cacheQuery[sqlOriginal]
pp.lock.Unlock()
if ok {
*sql = v
return nil
}
if !strings.HasPrefix(sqlOriginal, "SELECT ") {
return nil
}
idxFrom := strings.Index(sqlOriginal, " FROM ")
if idxFrom < 0 {
return nil
}
fromTableName := strings.Split(strings.TrimSpace(sqlOriginal[idxFrom+len(" FROM"):]), " ")[0]
sels := strings.TrimSpace(sqlOriginal[len("SELECT "):idxFrom])
split := strings.Split(sels, ",")
newsel := make([]string, 0)
aliasMap := make(map[string]string)
2023-01-15 06:30:30 +01:00
for _, v := range regexAlias.MatchAll(sqlOriginal) {
aliasMap[strings.TrimSpace(v.GroupByIndex(2).Value())] = strings.TrimSpace(v.GroupByIndex(1).Value())
}
for _, expr := range split {
expr = strings.TrimSpace(expr)
if expr == "*" {
columns, ok := pp.dbColumns[fromTableName]
if !ok {
return errors.New(fmt.Sprintf("[preprocessor]: table '%s' not found", fromTableName))
}
for _, colname := range columns {
newsel = append(newsel, fmt.Sprintf("%s.%s AS \"%s\"", fromTableName, colname, colname))
}
} else if strings.HasSuffix(expr, ".*") {
tableName := expr[0 : len(expr)-2]
if tableRealName, ok := aliasMap[tableName]; ok {
columns, ok := pp.dbColumns[tableRealName]
if !ok {
return errors.New(fmt.Sprintf("[sql-preprocessor]: table '%s' not found", tableRealName))
}
for _, colname := range columns {
newsel = append(newsel, fmt.Sprintf("%s.%s AS \"%s.%s\"", tableName, colname, tableName, colname))
}
} else if tableName == fromTableName {
columns, ok := pp.dbColumns[tableName]
if !ok {
return errors.New(fmt.Sprintf("[sql-preprocessor]: table '%s' not found", tableName))
}
for _, colname := range columns {
newsel = append(newsel, fmt.Sprintf("%s.%s AS \"%s\"", tableName, colname, colname))
}
} else {
columns, ok := pp.dbColumns[tableName]
if !ok {
return errors.New(fmt.Sprintf("[sql-preprocessor]: table '%s' not found", tableName))
}
for _, colname := range columns {
newsel = append(newsel, fmt.Sprintf("%s.%s AS \"%s.%s\"", tableName, colname, tableName, colname))
}
}
} else {
return nil
}
}
newSQL := "SELECT " + strings.Join(newsel, ", ") + sqlOriginal[idxFrom:]
pp.lock.Lock()
pp.cacheQuery[sqlOriginal] = newSQL
pp.lock.Unlock()
2022-12-23 20:27:21 +01:00
log.Debug().Msgf("Preprocessed SQL statement from\n'%s'\n--to-->\n'%s'", sqlOriginal, newSQL)
*sql = newSQL
return nil
}
func (pp *DBPreprocessor) PreExec(ctx context.Context, txID *uint16, sql *string, params *sq.PP) error {
return nil
}
func (pp *DBPreprocessor) PostPing(result error) {
//
}
func (pp *DBPreprocessor) PostTxBegin(txid uint16, result error) {
//
}
func (pp *DBPreprocessor) PostTxCommit(txid uint16, result error) {
//
}
func (pp *DBPreprocessor) PostTxRollback(txid uint16, result error) {
//
}
func (pp *DBPreprocessor) PostQuery(txID *uint16, sqlOriginal string, sqlReal string, params sq.PP) {
//
}
func (pp *DBPreprocessor) PostExec(txID *uint16, sqlOriginal string, sqlReal string, params sq.PP) {
//
}