metadata

Documentation

Overview

Package metadata caches the server objects that completion needs: databases, tables, columns, functions and friends. The cache is filled from system tables in the background; readers always get an immutable snapshot and never wait for the server.

Index

• func TableKey(database, table string) string
• type Cache
  • func NewCache(q Querier) *Cache
  • func (c *Cache) LastError() error
  • func (c *Cache) Refresh(ctx context.Context) error
  • func (c *Cache) RefreshAsync()
  • func (c *Cache) RefreshIfOlder(maxAge time.Duration)
  • func (c *Cache) Snapshot() *Snapshot
• type Column
• type Function
• type Querier
• type Snapshot
  • func (s *Snapshot) HasDatabase(name string) bool
• type Table
  • func (t Table) Kind() string

Functions

func TableKey

func TableKey(database, table string) string

TableKey is the key of Snapshot.Columns.

Types

type Cache

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

Cache holds the current snapshot and refreshes it on demand.

func NewCache

func NewCache(q Querier) *Cache

NewCache creates a cache that loads through q.

func (*Cache) LastError

func (c *Cache) LastError() error

LastError returns the error of the most recent refresh, if it had one.

func (*Cache) Refresh

func (c *Cache) Refresh(ctx context.Context) error

Refresh reloads the metadata and waits for the result.

func (*Cache) RefreshAsync

func (c *Cache) RefreshAsync()

RefreshAsync starts a background refresh unless one is already running, in which case one more refresh is queued so that the request is not lost.

func (*Cache) RefreshIfOlder

func (c *Cache) RefreshIfOlder(maxAge time.Duration)

RefreshIfOlder starts a background refresh when the snapshot is older than maxAge.

func (*Cache) Snapshot

func (c *Cache) Snapshot() *Snapshot

Snapshot returns the current metadata. It never blocks and never returns nil.

type Column

type Column struct {
	Name string
	Type string
}

Column is a table column.

type Function

type Function struct {
	Name      string
	Aggregate bool
}

Function is a SQL function.

type Querier

type Querier interface {
	QueryStrings(ctx context.Context, sql string) ([][]string, error)
}

Querier runs a metadata query and returns all values as strings.

type Snapshot

type Snapshot struct {
	Databases      []string
	Tables         map[string][]Table  // by database
	Columns        map[string][]Column // by TableKey
	Functions      []Function
	TableFunctions []string
	DataTypes      []string
	Engines        []string
	Formats        []string
	Settings       []string
	Keywords       []string
	// LoadedAt is when the snapshot was fetched; zero for the built-in fallback.
	LoadedAt time.Time
}

Snapshot is an immutable view of the cached metadata.

func (*Snapshot) HasDatabase

func (s *Snapshot) HasDatabase(name string) bool

HasDatabase reports whether a database with this exact name is known.

type Table

type Table struct {
	Database string
	Name     string
	Engine   string
}

Table is a table-like object: a table, view or dictionary.

func (Table) Kind

func (t Table) Kind() string

Kind classifies the table by its engine: "view", "dictionary" or "table".