database

package
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 Go to latest Published: May 24, 2021 License: MIT Imports: 12 Imported by: 0

Documentation

Overview

Package database provides database primitives such as tables, transactions and indexes.

Index

Constants

This section is empty.

Variables

View Source 
var (
	// ErrIndexDuplicateValue is returned when a value is already associated with a key
	ErrIndexDuplicateValue = errors.New("duplicate value")

	// ErrIndexWrongArity is returned when trying to index more values that what an
	// index supports.
	ErrIndexWrongArity = errors.New("wrong index arity")
)

Functions

func CastConversion 

func CastConversion(v document.Value, path document.Path, targetType document.ValueType) (document.Value, error)

CastConversion is a ConversionFunc that casts the value to the target type.

func LosslessNumbersConversion 

func LosslessNumbersConversion(v document.Value, path document.Path, targetType document.ValueType) (document.Value, error)

LosslessConversion is a ConversionFunc that only converts numbers if there is no precision loss in the process.

Types

type Catalog 

type Catalog struct {
	// contains filtered or unexported fields
}

Catalog holds all table and index informations.

func NewCatalog 

func NewCatalog() *Catalog

func (*Catalog) AddFieldConstraint 

func (c *Catalog) AddFieldConstraint(tx *Transaction, tableName string, fc FieldConstraint) error

AddFieldConstraint adds a field constraint to a table.

func (*Catalog) Clone 

func (c *Catalog) Clone() *Catalog

Clone the catalog. Mostly used for testing purposes.

func (*Catalog) CreateIndex 

func (c *Catalog) CreateIndex(tx *Transaction, info *IndexInfo) error

CreateIndex creates an index with the given name. If it already exists, returns errs.ErrIndexAlreadyExists.

func (*Catalog) CreateTable 

func (c *Catalog) CreateTable(tx *Transaction, tableName string, info *TableInfo) error

CreateTable creates a table with the given name. If it already exists, returns ErrTableAlreadyExists.

func (*Catalog) DropIndex 

func (c *Catalog) DropIndex(tx *Transaction, name string) error

DropIndex deletes an index from the database.

func (*Catalog) DropTable 

func (c *Catalog) DropTable(tx *Transaction, tableName string) error

DropTable deletes a table from the

func (*Catalog) GetIndex 

func (c *Catalog) GetIndex(tx *Transaction, indexName string) (*Index, error)

GetIndex returns an index by name.

func (*Catalog) GetTable 

func (c *Catalog) GetTable(tx *Transaction, tableName string) (*Table, error)

func (*Catalog) ListIndexes 

func (c *Catalog) ListIndexes(tableName string) []string

ListIndexes returns an index by name.

func (*Catalog) Load 

func (c *Catalog) Load(tables []TableInfo, indexes []IndexInfo)

func (*Catalog) ReIndex 

func (c *Catalog) ReIndex(tx *Transaction, indexName string) error

ReIndex truncates and recreates selected index from scratch.

func (*Catalog) ReIndexAll 

func (c *Catalog) ReIndexAll(tx *Transaction) error

ReIndexAll truncates and recreates all indexes of the database from scratch.

func (*Catalog) RenameTable 

func (c *Catalog) RenameTable(tx *Transaction, oldName, newName string) error

RenameTable renames a table. If it doesn't exist, it returns errs.ErrTableNotFound.

type ConversionFunc 

type ConversionFunc func(v document.Value, path document.Path, targetType document.ValueType) (document.Value, error)

ConversionFunc is called when the type of a value is different than the expected type and the value needs to be converted.

type Database 

type Database struct {

	// Codec used to encode documents. Defaults to MessagePack.
	Codec encoding.Codec

	Catalog *Catalog
	// contains filtered or unexported fields
}

A Database manages a list of tables in an engine.

func New 

func New(ctx context.Context, ng engine.Engine, opts Options) (*Database, error)

New initializes the DB using the given engine.

func (*Database) Begin 

func (db *Database) Begin(writable bool) (*Transaction, error)

Begin starts a new transaction with default options. The returned transaction must be closed either by calling Rollback or Commit.

func (*Database) BeginTx 

func (db *Database) BeginTx(ctx context.Context, opts *TxOptions) (*Transaction, error)

BeginTx starts a new transaction with the given options. If opts is empty, it will use the default options. The returned transaction must be closed either by calling Rollback or Commit. If the Attached option is passed, it opens a database level transaction, which gets attached to the database and prevents any other transaction to be opened afterwards until it gets rolled back or commited.

func (*Database) Close 

func (db *Database) Close() error

Close the underlying engine.

func (*Database) GetAttachedTx 

func (db *Database) GetAttachedTx() *Transaction

GetAttachedTx returns the transaction attached to the database. It returns nil if there is no such transaction. The returned transaction is not thread safe.

type FieldConstraint 

type FieldConstraint struct {
	Path         document.Path
	Type         document.ValueType
	IsPrimaryKey bool
	IsNotNull    bool
	IsUnique     bool // not stored, only set during table creation
	DefaultValue document.Value
	IsInferred   bool
	InferredBy   []document.Path
}

FieldConstraint describes constraints on a particular field.

func (*FieldConstraint) HasDefaultValue 

func (f *FieldConstraint) HasDefaultValue() bool

HasDefaultValue returns this field contains a default value constraint.

func (*FieldConstraint) IsEqual 

func (f *FieldConstraint) IsEqual(other *FieldConstraint) (bool, error)

IsEqual compares f with other member by member. Inference is not compared.

func (*FieldConstraint) MergeInferred 

func (f *FieldConstraint) MergeInferred(other *FieldConstraint)

MergeInferred adds the other.InferredBy to f.InferredBy and ensures there are no duplicates.

func (*FieldConstraint) ScanDocument 

func (f *FieldConstraint) ScanDocument(d document.Document) error

ScanDocument implements the document.Scanner interface.

func (*FieldConstraint) String 

func (f *FieldConstraint) String() string

func (*FieldConstraint) ToDocument 

func (f *FieldConstraint) ToDocument() document.Document

ToDocument returns a document from f.

type FieldConstraints 

type FieldConstraints []*FieldConstraint

FieldConstraints is a list of field constraints.

func NewFieldConstraints 

func NewFieldConstraints(userConstraints []*FieldConstraint) (FieldConstraints, error)

NewFieldConstraints takes user-defined field constraints, validates them, infers additional constraints if needed, and returns a valid FieldConstraints type that can be assigned to a table.

func (*FieldConstraints) Add 

func (f *FieldConstraints) Add(newFc *FieldConstraint) error

Add a field constraint to the list. If another constraint exists for the same path and they are equal, newFc will be ignored. Otherwise an error will be returned. If newFc has been inferred by another constraint and another constraint exists with the same path, their InferredBy member will be merged.

func (FieldConstraints) ConvertDocument 

func (f FieldConstraints) ConvertDocument(d document.Document) (*document.FieldBuffer, error)

ConvertDocument the document using the field constraints. It converts any path that has a field constraint on it into the specified type using CAST. If there is no constraint on an integer field or value, it converts it into a double. Default values on missing fields are not applied.

func (FieldConstraints) ConvertValueAtPath 

func (f FieldConstraints) ConvertValueAtPath(path document.Path, v document.Value, conversionFn ConversionFunc) (document.Value, error)

ConvertValueAtPath converts the value using the field constraints that are applicable at the given path.

func (FieldConstraints) Get 

func (f FieldConstraints) Get(path document.Path) *FieldConstraint

Get a field constraint by path. Returns nil if not found.

func (FieldConstraints) Infer 

func (f FieldConstraints) Infer() (FieldConstraints, error)

Infer additional constraints based on user defined ones. For example, given the following table: 

CREATE TABLE foo (a.b[0] TEXT)

this function will return a TableInfo that behaves as if the table had been created like this: 

CREATE TABLE foo(
   a DOCUMENT
   a.b ARRAY
   a.b[0] TEXT
)

func (FieldConstraints) ValidateDocument 

func (f FieldConstraints) ValidateDocument(d document.Document) (*document.FieldBuffer, error)

ValidateDocument calls Convert then ensures the document validates against the field constraints.

type Index 

type Index struct {
	Info *IndexInfo
	// contains filtered or unexported fields
}

An Index associates encoded values with keys.

The association is performed by encoding the values in a binary format that preserve ordering when compared lexicographically. For the implementation, see the binarysort package and the document.ValueEncoder.

func NewIndex 

func NewIndex(tx engine.Transaction, idxName string, opts *IndexInfo) *Index

NewIndex creates an index that associates values with a list of keys.

func (*Index) Arity 

func (idx *Index) Arity() int

Arity returns how many values the index is operating on. For example, an index created with `CREATE INDEX idx_a_b ON foo (a, b)` has an arity of 2.

func (*Index) AscendGreaterOrEqual 

func (idx *Index) AscendGreaterOrEqual(pivot Pivot, fn func(val, key []byte) error) error

AscendGreaterOrEqual seeks for the pivot and then goes through all the subsequent key value pairs in increasing order and calls the given function for each pair. If the given function returns an error, the iteration stops and returns that error. If the pivot(s) is/are empty, starts from the beginning.

Valid pivots are: - zero value pivot

  • iterate on everything

- n elements pivot (where n is the index arity) with each element having a value and a type

  • iterate starting at the closest index value
  • optionally, the last pivot element can have just a type and no value, which will scope the value of that element to that type

- less than n elements pivot, with each element having a value and a type

  • iterate starting at the closest index value, using the first known value for missing elements
  • optionally, the last pivot element can have just a type and no value, which will scope the value of that element to that type

- a single element with a type but nil value: will iterate on everything of that type

Any other variation of a pivot are invalid and will panic.

func (*Index) Delete 

func (idx *Index) Delete(vs []document.Value, k []byte) error

Delete all the references to the key from the index.

func (*Index) DescendLessOrEqual 

func (idx *Index) DescendLessOrEqual(pivot Pivot, fn func(val, key []byte) error) error

DescendLessOrEqual seeks for the pivot and then goes through all the subsequent key value pairs in descreasing order and calls the given function for each pair. If the given function returns an error, the iteration stops and returns that error. If the pivot(s) is/are empty, starts from the end.

Valid pivots are: - zero value pivot

  • iterate on everything

- n elements pivot (where n is the index arity) with each element having a value and a type

  • iterate starting at the closest index value
  • optionally, the last pivot element can have just a type and no value, which will scope the value of that element to that type

- less than n elements pivot, with each element having a value and a type

  • iterate starting at the closest index value, using the last known value for missing elements
  • optionally, the last pivot element can have just a type and no value, which will scope the value of that element to that type

- a single element with a type but nil value: will iterate on everything of that type

Any other variation of a pivot are invalid and will panic.

func (*Index) EncodeValueBuffer 

func (idx *Index) EncodeValueBuffer(vb *document.ValueBuffer) ([]byte, error)

EncodeValueBuffer encodes the value buffer containing a single or multiple values being indexed into a byte array, keeping the order of the original values.

The values are marshalled and separated with a document.ArrayValueDelim, *without* a trailing document.ArrayEnd, which enables to handle cases where only some of the values are being provided and still perform lookups (like index_foo_a_b_c and providing only a and b).

See IndexValueEncoder for details about how the value themselves are encoded.

func (*Index) IsComposite 

func (idx *Index) IsComposite() bool

IsComposite returns true if the index is defined to operate on at least more than one value.

func (*Index) Papity added in v0.1.1 

func (idx *Index) Papity() int

func (*Index) Set 

func (idx *Index) Set(vs []document.Value, k []byte) error

Set associates values with a key. If Unique is set to false, it is possible to associate multiple keys for the same value but a key can be associated to only one value.

func (*Index) Truncate 

func (idx *Index) Truncate() error

Truncate deletes all the index data.

type IndexInfo 

type IndexInfo struct {
	TableName string
	IndexName string
	Paths     []document.Path

	// If set to true, values will be associated with at most one key. False by default.
	Unique bool

	// If set, the index is typed and only accepts values of those types.
	Types []document.ValueType
}

IndexInfo holds the configuration of an index.

func (IndexInfo) Clone 

func (i IndexInfo) Clone() *IndexInfo

Clone returns a copy of the index information.

func (*IndexInfo) String 

func (i *IndexInfo) String() string

String returns a SQL representation.

func (*IndexInfo) ToDocument 

func (i *IndexInfo) ToDocument() document.Document

ToDocument creates a document from an IndexConfig.

type Indexes 

type Indexes []*Index

func (Indexes) GetIndex 

func (i Indexes) GetIndex(name string) *Index

func (Indexes) GetIndexByPath 

func (i Indexes) GetIndexByPath(p document.Path) *Index

type Options 

type Options struct {
	Codec encoding.Codec
}

type Pivot 

type Pivot []document.Value

func (Pivot) IsAny 

func (pivot Pivot) IsAny() bool

IsAny return true if every value of the pivot is typed with AnyType

type Table 

type Table struct {
	Tx    *Transaction
	Store engine.Store
	Name  string
	// Table information.
	// May not represent the most up to date data.
	// Always get a fresh Table instance before relying on this field.
	Info *TableInfo
	// List of Indexes of this table.
	// May not represent the most up to date data.
	// Always get a fresh Table instance relying on this field.
	Indexes Indexes
}

A Table represents a collection of documents.

func GetIndexStore 

func GetIndexStore(tx *Transaction) *Table

func GetTableStore 

func GetTableStore(tx *Transaction) *Table

func (*Table) AscendGreaterOrEqual 

func (t *Table) AscendGreaterOrEqual(pivot document.Value, fn func(d document.Document) error) error

AscendGreaterOrEqual iterates over the documents of the table whose key is greater than or equal to the pivot. The pivot is converted to the type of the primary key, if any, prior to iteration. If the pivot is empty, it iterates from the beginning of the table.

func (*Table) Delete 

func (t *Table) Delete(key []byte) error

Delete a document by key. Indexes are automatically updated.

func (*Table) DescendLessOrEqual 

func (t *Table) DescendLessOrEqual(pivot document.Value, fn func(d document.Document) error) error

DescendLessOrEqual iterates over the documents of the table whose key is less than or equal to the pivot, in reverse order. The pivot is converted to the type of the primary key, if any, prior to iteration. If the pivot is empty, it iterates from the end of the table in reverse order.

func (*Table) EncodeValue 

func (t *Table) EncodeValue(v document.Value) ([]byte, error)

EncodeValue encodes a value following primary key constraints. It returns a binary representation of the key as used in the store. It can be used to manually add a new entry to the store or to compare with other keys during table iteration.

func (*Table) GetDocument 

func (t *Table) GetDocument(key []byte) (document.Document, error)

GetDocument returns one document by key.

func (*Table) Insert 

func (t *Table) Insert(d document.Document) (document.Document, error)

Insert the document into the table. If a primary key has been specified during the table creation, the field is expected to be present in the given document. If no primary key has been selected, a monotonic autoincremented integer key will be generated. It returns the inserted document alongside its key. They key can be accessed using the document.Keyer interface.

func (*Table) Iterate 

func (t *Table) Iterate(fn func(d document.Document) error) error

Iterate goes through all the documents of the table and calls the given function by passing each one of them. If the given function returns an error, the iteration stops.

func (*Table) Replace 

func (t *Table) Replace(key []byte, d document.Document) error

Replace a document by key. An error is returned if the key doesn't exist. Indexes are automatically updated.

func (*Table) Truncate 

func (t *Table) Truncate() error

Truncate deletes all the documents from the table.

type TableInfo 

type TableInfo struct {
	// name of the table.
	TableName string
	// name of the store associated with the table.
	StoreName []byte
	ReadOnly  bool

	FieldConstraints FieldConstraints
}

TableInfo contains information about a table.

func (*TableInfo) Clone 

func (ti *TableInfo) Clone() *TableInfo

Clone creates another tableInfo with the same values.

func (*TableInfo) GetPrimaryKey 

func (ti *TableInfo) GetPrimaryKey() *FieldConstraint

GetPrimaryKey returns the field constraint of the primary key. Returns nil if there is no primary key.

func (*TableInfo) String 

func (ti *TableInfo) String() string

String returns a SQL representation.

func (*TableInfo) ToDocument 

func (ti *TableInfo) ToDocument() document.Document

ToDocument turns ti into a document.

type Transaction 

type Transaction struct {
	DB       *Database
	Tx       engine.Transaction
	Catalog  *Catalog
	Writable bool

	// these functions are run after a successful rollback.
	OnRollbackHooks []func()
	// contains filtered or unexported fields
}

Transaction represents a database transaction. It provides methods for managing the collection of tables and the transaction itself. Transaction is either read-only or read/write. Read-only can be used to read tables and read/write can be used to read, create, delete and modify tables.

func (*Transaction) Commit 

func (tx *Transaction) Commit() error

Commit the transaction. Calling this method on read-only transactions will return an error.

func (*Transaction) Rollback 

func (tx *Transaction) Rollback() error

Rollback the transaction. Can be used safely after commit.

type TxOptions 

type TxOptions struct {
	// Open a read-only transaction.
	ReadOnly bool
	// Set the transaction as global at the database level.
	// Any queries run by the database will use that transaction until it is
	// rolled back or commited.
	Attached bool
}

TxOptions are passed to Begin to configure transactions.

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