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sqlclone.go
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sqlclone.go
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package sqlclone
import (
"crypto/sha256"
"database/sql"
"encoding/hex"
"fmt"
"sort"
"strings"
_ "github.com/lib/pq"
)
type DatabaseDump map[string][]map[string]string
type Mapping map[string]map[string]string
// gets all related rows of the starting points as specified in the download options from source database
// returns collected data as a DatabaseDump of the structure: map[string][]map[string]string
func Download(db database, options *downloadOptions) (DatabaseDump, error) {
references, err := db.getReferences()
if err != nil {
return nil, err
}
dumpCache := make(map[string]bool, 0)
queryCache := make(map[string]bool, 0)
databaseDump := make(DatabaseDump)
for _, sp := range options.start_points {
databaseDump, dumpCache, queryCache, err = getDataRecursively(db, references, databaseDump, dumpCache, queryCache, options.dont_recurse, sp.table, sp.column, sp.value)
}
return databaseDump, err
}
func getDataRecursively(db database, references References, databaseDump DatabaseDump, dumpCache map[string]bool, queryCache map[string]bool, dont_recurse []string, table_name string, col string, val string) (DatabaseDump, map[string]bool, map[string]bool, error) {
rows, err := db.getRows(table_name, col, val)
queryCache[query_hash(table_name, col, val)] = true
if err != nil {
return nil, nil, nil, err
}
for _, r := range rows {
rowSummary := row_hash(table_name, r)
_, ok := dumpCache[rowSummary]
if !ok {
databaseDump[table_name] = append(databaseDump[table_name], r)
dumpCache[rowSummary] = true
var df = getReferencesFromTable(references, table_name)
for _, d := range df {
_, ok := queryCache[query_hash(d.referenced_table_name, d.referenced_column_name, r[d.column_name])]
if !ok {
getDataRecursively(db, references, databaseDump, dumpCache, queryCache, dont_recurse, d.referenced_table_name, d.referenced_column_name, r[d.column_name])
}
}
var dr = getReferencesToTable(references, table_name)
for _, d := range dr {
_, ok := queryCache[query_hash(d.table_name, d.column_name, val)]
if !ok && !sliceContains(dont_recurse, d.table_name) {
getDataRecursively(db, references, databaseDump, dumpCache, queryCache, dont_recurse, d.table_name, d.column_name, r[d.referenced_column_name])
}
}
}
}
return databaseDump, dumpCache, queryCache, nil
}
func Upload(db database, data DatabaseDump) (Mapping, error) {
tx, err := db.newTransaction()
if err != nil {
return nil, err
}
mapping, err := upload(tx, db, data)
if err != nil {
tx.Rollback()
return nil, fmt.Errorf("could not complete insertion: %s", err)
}
// if all inserts succeeded, commit the transaction
err = tx.Commit()
if err != nil {
return mapping, fmt.Errorf("commit failed: %q", err)
}
return mapping, nil
}
// inserts all downloaded rows in the DatabaseDump into target database
// returns a map of the structure map[string]map[string]string showing which identifiers in source database correspond to which identifiers in target database
func upload(tx *sql.Tx, db database, data DatabaseDump) (Mapping, error) {
order, err := db.getDependencyOrder()
if err != nil {
return nil, err
}
references, err := db.getReferences()
if err != nil {
return nil, err
}
primaryKeys, err := db.getPrimaryKeys()
if err != nil {
return nil, err
}
mapping := make(Mapping)
for _, t := range order {
ok, c := isTableSelfReferencing(references, t)
if ok {
sort.Slice(data[t], func(i, j int) bool {
v1 := fmt.Sprintf("%v", data[t][i][c])
v2 := fmt.Sprintf("%v", data[t][j][c])
return v1 < v2
})
}
for _, r := range data[t] {
mapping, err = uploadRow(db, tx, primaryKeys, references, mapping, t, r)
if err != nil {
return nil, fmt.Errorf("upload could not be completed: %q", err)
}
}
}
return mapping, nil
}
// insert a row into the target database and update the mapping if necessary
func uploadRow(db database, tx *sql.Tx, primaryKeys map[string][]string, references References, mapping Mapping, table_name string, data map[string]string) (Mapping, error) {
columns := make([]string, 0)
primary_key := ""
for key := range data {
if !sliceContains(primaryKeys[table_name], key) {
columns = append(columns, key)
} else {
primary_key = key // column that has an auto value
}
}
values := make([]string, 0)
for _, key := range columns {
d, exists := getReference(references[table_name], key)
if exists && data[key] != "<nil>" {
// column contains a value that references another table
// --> we need to use the updated value in the reference map
ids, exists := mapping[d.referenced_table_name]
if exists {
values = append(values, ids[fmt.Sprintf("%v", data[key])])
} else {
// should never be the case as we put the new ids into mapping, but just in case this would use the old value
// todo: should we abort with error message?
values = append(values, data[key])
}
} else {
values = append(values, data[key])
}
}
lastInsertId, err := db.insertRow(tx, table_name, columns, values, primary_key)
if err != nil {
return mapping, err
}
if lastInsertId != -1 {
// update mapping
ids, exists := mapping[table_name]
if exists {
ids[fmt.Sprintf("%v", data["id"])] = fmt.Sprintf("%d", lastInsertId)
} else {
// first entry
mapping[table_name] = map[string]string{fmt.Sprintf("%v", data["id"]): fmt.Sprintf("%d", lastInsertId)}
}
}
return mapping, nil
}
// ----------------------------
// ----- HELPER FUNCTIONS -----
// ----------------------------
func row_hash(table_name string, data map[string]string) string {
h := table_name
sortedKeys := make([]string, 0)
for k := range data {
sortedKeys = append(sortedKeys, k)
}
sort.Strings(sortedKeys)
values := make([]string, 0)
values = append(values, table_name)
for _, k := range sortedKeys {
h += data[k]
values = append(values, data[k])
}
hasher := sha256.New()
hasher.Write([]byte(strings.Join(values, "|")))
hash := hex.EncodeToString(hasher.Sum(nil))
return hash
}
func query_hash(table_name string, colum_name string, value string) string {
values := make([]string, 0)
values = append(values, table_name)
values = append(values, colum_name)
values = append(values, value)
hasher := sha256.New()
hasher.Write([]byte(strings.Join(values, "|")))
hash := hex.EncodeToString(hasher.Sum(nil))
return hash
}
func sliceContains(mySlice []string, searchString string) bool {
for _, s := range mySlice {
if s == searchString {
return true
}
}
return false
}