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database.go
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database.go
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package db
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"math/bits"
"strings"
)
const (
headerMagic = "SQLite format 3\x00"
headerSize = 100
// CachePages is the number of pages to keep in memory. Default size per
// page is 4K (1K on older databases).
CachePages = 100
)
var (
// Various error messages returned when the database is corrupted
ErrInvalidMagic = errors.New("invalid magic number")
ErrInvalidPageSize = errors.New("invalid page size")
ErrReservedSpace = errors.New("unsupported database (encrypted?)")
ErrCorrupted = errors.New("database corrupted")
ErrInvalidDef = errors.New("invalid object definition")
ErrRecursion = errors.New("tree is too deep")
// Various error messages returned when the database uses features sqlittle
// doesn't support.
ErrIncompatible = errors.New("incompatible database version")
ErrEncoding = errors.New("unsupported encoding")
// Database is in WAL journal mode, which we don't support. You need to
// convert the database to journal mode.
ErrWAL = errors.New("WAL journal mode is unsupported")
// There is a stale `-journal` file present with an unfinished transaction.
// Open the database in sqlite3 to repair the database.
ErrHotJournal = errors.New("crashed transaction present")
ErrNoSuchTable = errors.New("no such table")
ErrNoSuchIndex = errors.New("no such index")
)
type header struct {
// The database page size in bytes.
PageSize int
// Updated when anything changes (only for non-WAL files).
ChangeCounter uint32
// Updated when any table definition changes
SchemaCookie uint32
}
type objectCache struct {
objects []sqliteMaster
err error
}
type Database struct {
journal string
dirty bool // reload header if true
l pager
header *header
btreeCache *btreeCache // table and index page cache
objectCache *objectCache
}
// OpenFile opens a .sqlite file. This is the main entry point.
// Use database.Close() when done.
func OpenFile(f string) (*Database, error) {
l, err := newFilePager(f)
if err != nil {
return nil, err
}
return newDatabase(l, f+"-journal")
}
func newDatabase(l pager, journal string) (*Database, error) {
d := &Database{
journal: journal,
dirty: true,
l: l,
btreeCache: newBtreeCache(CachePages),
}
return d, d.resolveDirty()
}
// Close the database.
func (db *Database) Close() error {
return db.l.Close()
}
// Lock database for reading. Blocks. Don't nest RLock() calls.
func (db *Database) RLock() error {
db.dirty = true
return db.l.RLock()
}
// Unlock a read lock. Use a single RUnlock() for every RLock().
func (db *Database) RUnlock() error {
return db.l.RUnlock()
}
// n starts at 1, sqlite style
func (db *Database) page(id int) ([]byte, error) {
if id < 1 {
return nil, errors.New("invalid page number")
}
return db.l.page(id, db.header.PageSize)
}
// the file header, as described in "1.2. The Database Header"
func parseHeader(b []byte) (header, error) {
hs := struct {
Magic [16]byte
PageSize uint16
_ uint8 // WriteVersion
ReadVersion uint8
ReservedSpace uint8
MaxFraction uint8
MinFraction uint8
LeafFraction uint8
ChangeCounter uint32
_ uint32
_ uint32
_ uint32
SchemaCookie uint32
SchemaFormat uint32
_ uint32
_ uint32
TextEncoding uint32
_ uint32
_ uint32
_ uint32
ReservedForExpansion [20]byte
_ uint32
_ uint32
}{}
if err := binary.Read(bytes.NewBuffer(b), binary.BigEndian, &hs); err != nil {
return header{}, err
}
h := header{}
if string(hs.Magic[:]) != headerMagic {
return h, ErrInvalidMagic
}
{
s := uint(hs.PageSize)
if s == 1 {
s = 1 << 16
}
isPower := func(n uint) bool {
return bits.OnesCount(n) == 1
}
if s < 512 || s > 1<<16 || !isPower(s) {
return header{}, ErrInvalidPageSize
}
h.PageSize = int(s)
}
switch hs.ReadVersion {
case 1:
// journal mode
case 2:
// we don't support WAL
return h, ErrWAL
default:
return h, ErrIncompatible
}
if int(hs.ReservedSpace) != 0 {
return h, ErrReservedSpace
}
if hs.MaxFraction != 64 ||
hs.MinFraction != 32 ||
hs.LeafFraction != 32 {
return h, ErrIncompatible
}
h.ChangeCounter = hs.ChangeCounter
h.SchemaCookie = hs.SchemaCookie
// 1,2,3,4 are the only valid values.
switch hs.SchemaFormat {
case 1:
// Version 1 ignores 'DESC' on indexes.
return h, ErrIncompatible
case 2, 3, 4:
default:
return h, ErrIncompatible
}
switch hs.TextEncoding {
case 1:
// UTF8. It's the only thing we currently support
case 2, 3:
// UTF16le and UTF16be
return h, ErrEncoding
default:
return h, ErrIncompatible
}
for _, v := range hs.ReservedForExpansion {
if v != 0 {
return h, ErrIncompatible
}
}
return h, nil
}
func (db *Database) resolveDirty() error {
if !db.dirty {
return nil
}
if db.journal != "" {
hot, err := validJournal(db.journal)
if err != nil {
return err
}
if hot {
// If something is using the transaction the db will have a RESERVED
// lock.
locked, err := db.l.CheckReservedLock()
if err != nil {
return err
}
if !locked {
return ErrHotJournal
}
}
}
buf, err := db.l.page(1, headerSize)
if err != nil {
return err
}
newHeader, err := parseHeader(buf)
if err != nil {
return err
}
if db.header != nil && db.header.ChangeCounter != newHeader.ChangeCounter {
db.btreeCache.clear()
}
if db.header != nil && db.header.SchemaCookie != newHeader.SchemaCookie {
db.objectCache = nil
}
db.dirty = false
db.header = &newHeader
return nil
}
// master records are defined as:
// CREATE TABLE sqlite_master(
// type text,
// name text,
// tbl_name text,
// rootpage integer,
// sql text
// );
type sqliteMaster struct {
typ, name, tblName string
rootPage int
sql string
}
func (db *Database) master() ([]sqliteMaster, error) {
if err := db.resolveDirty(); err != nil {
return nil, err
}
if o := db.objectCache; o != nil {
return o.objects, o.err
}
master, err := db.openTable(1)
if err != nil {
return nil, err
}
var objects []sqliteMaster
_, err = master.Iter(maxRecursion, db, func(rowid int64, pl cellPayload) (bool, error) {
c, err := addOverflow(db, pl)
if err != nil {
return false, err
}
e, err := parseRecord(c)
if err != nil {
return false, err
}
if len(e) != 5 {
return false, ErrInvalidDef
}
m := sqliteMaster{}
if s, ok := e[0].(string); !ok {
return false, ErrInvalidDef
} else {
m.typ = s
}
if s, ok := e[1].(string); !ok {
return false, ErrInvalidDef
} else {
m.name = strings.ToLower(s)
}
if s, ok := e[2].(string); !ok {
return false, ErrInvalidDef
} else {
m.tblName = strings.ToLower(s)
}
if n, ok := e[3].(int64); !ok {
return false, ErrInvalidDef
} else {
m.rootPage = int(n)
}
switch s := e[4].(type) {
case string:
m.sql = s
case nil:
default:
return false, ErrInvalidDef
}
objects = append(objects, m)
return false, nil
})
db.objectCache = &objectCache{
objects: objects,
err: err,
}
return objects, err
}
// openPage returns a tableBtree or indexBtree
func (db *Database) openPage(page int) (interface{}, error) {
if err := db.resolveDirty(); err != nil {
return nil, err
}
if p := db.btreeCache.get(page); p != nil {
return p, nil
}
buf, err := db.page(page)
if err != nil {
return nil, err
}
p, err := newBtree(buf, page == 1, db.header.PageSize)
if err == nil {
db.btreeCache.set(page, p)
}
return p, err
}
func (db *Database) openTable(page int) (tableBtree, error) {
p, err := db.openPage(page)
if err != nil {
return nil, err
}
tb, ok := p.(tableBtree)
if !ok {
return nil, errors.New("found an index, expected a table")
}
return tb, nil
}
func (db *Database) openIndex(page int) (indexBtree, error) {
p, err := db.openPage(page)
if err != nil {
return nil, err
}
tb, ok := p.(indexBtree)
if !ok {
return nil, errors.New("found a table, expected an index")
}
return tb, nil
}
// Tables lists all table names. Also sqlite internal ones.
func (db *Database) Tables() ([]string, error) {
return db.objectNames("table")
}
// Indexes lists all index names.
func (db *Database) Indexes() ([]string, error) {
return db.objectNames("index")
}
func (db *Database) objectNames(typ string) ([]string, error) {
objects, err := db.master()
if err != nil {
return nil, err
}
var names []string
for _, o := range objects {
if o.typ == typ {
names = append(names, o.name)
}
}
return names, nil
}
// withoutRowid is true if name is a 'WITHOUT ROWID' table
func (db *Database) withoutRowid(name string) bool {
t, err := db.Table(name)
if err != nil {
return false
}
_, err = t.db.openIndex(t.root)
return err == nil
}
// Table opens the named table.
// Will return ErrNoSuchTable when the table isn't there (or isn't a table).
// Table pointer is always valid if err == nil.
// See also NonRowidTable() for `WITHOUT ROWID` tables.
func (db *Database) Table(name string) (*Table, error) {
objects, err := db.master()
if err != nil {
return nil, err
}
n := strings.ToLower(name)
for _, o := range objects {
if o.typ == "table" && o.name == n {
return &Table{db: db, root: o.rootPage, sql: o.sql}, nil
}
}
return nil, ErrNoSuchTable
}
// NonRowidTable open a `WITHOUT ROWID` table. It's implemented with an
// Index.
func (db *Database) NonRowidTable(name string) (*Index, error) {
objects, err := db.master()
if err != nil {
return nil, err
}
n := strings.ToLower(name)
for _, o := range objects {
if o.typ == "table" && o.name == n {
return &Index{db: db, root: o.rootPage, sql: o.sql}, nil
}
}
return nil, ErrNoSuchTable
}
// Index opens the named index.
// Will return ErrNoSuchIndex when the index isn't there (or isn't an index).
// Index pointer is always valid if err == nil.
//
// Indexes work for normal and WITHOUT ROWID tables. The columns the callback
// gets depends on the type of table.
func (db *Database) Index(name string) (*Index, error) {
objects, err := db.master()
if err != nil {
return nil, err
}
n := strings.ToLower(name)
for _, o := range objects {
if o.typ == "index" && o.name == n {
return &Index{db: db, root: o.rootPage, sql: o.sql}, nil
}
}
return nil, ErrNoSuchIndex
}
// Schema gives the definition of a table and all associated indexes.
func (db *Database) Schema(table string) (*Schema, error) {
m, err := db.master()
if err != nil {
return nil, err
}
return newSchema(table, m)
}
// Info gives some debugging info about the open database
func (db *Database) Info() (string, error) {
b := &strings.Builder{}
oo, err := db.master()
if err != nil {
return "", err
}
for _, o := range oo {
fmt.Fprintf(b, "- %s (%s)\n owner: %s\n sql: %s\n", o.name, o.typ, o.tblName, o.sql)
switch o.typ {
case "table":
switch db.withoutRowid(o.name) {
case false:
fmt.Fprintf(b, " first rows:\n")
t, err := db.Table(o.name)
if err != nil {
fmt.Fprintf(b, " error: %s\n", err)
continue
}
i := 0
if err := t.Scan(func(rowid int64, rec Record) bool {
fmt.Fprintf(b, " %d: %v\n", rowid, rec)
i++
return i > 5
}); err != nil {
fmt.Fprintf(b, " error: %s\n", err)
} else if i == 0 {
fmt.Fprintf(b, " (no rows)\n")
}
case true:
fmt.Fprintf(b, " (WITHOUT ROWID table)\n")
fmt.Fprintf(b, " first rows:\n")
t, err := db.NonRowidTable(o.name)
if err != nil {
fmt.Fprintf(b, " error: %s\n", err)
continue
}
i := 0
if err := t.Scan(func(rec Record) bool {
fmt.Fprintf(b, " %v\n", rec)
i++
return i > 5
}); err != nil {
fmt.Fprintf(b, " error: %s\n", err)
} else if i == 0 {
fmt.Fprintf(b, " (no rows)\n")
}
}
case "index":
fmt.Fprintf(b, " first rows:\n")
if ind, err := db.Index(o.name); err != nil {
fmt.Fprintf(b, " error: %s\n", err)
} else {
i := 0
ind.Scan(func(rec Record) bool {
fmt.Fprintf(b, " %v\n", rec)
i++
return i > 5
})
if i == 0 {
fmt.Fprintf(b, " (no rows)\n")
}
}
}
}
return b.String(), nil
}