mirror of https://github.com/jackc/pgx.git
113 lines
3.0 KiB
Go
113 lines
3.0 KiB
Go
package stmtcache
|
|
|
|
import (
|
|
"container/list"
|
|
|
|
"github.com/jackc/pgx/v5/pgconn"
|
|
)
|
|
|
|
// LRUCache implements Cache with a Least Recently Used (LRU) cache.
|
|
type LRUCache struct {
|
|
cap int
|
|
m map[string]*list.Element
|
|
l *list.List
|
|
invalidStmts []*pgconn.StatementDescription
|
|
}
|
|
|
|
// NewLRUCache creates a new LRUCache. cap is the maximum size of the cache.
|
|
func NewLRUCache(cap int) *LRUCache {
|
|
return &LRUCache{
|
|
cap: cap,
|
|
m: make(map[string]*list.Element),
|
|
l: list.New(),
|
|
}
|
|
}
|
|
|
|
// Get returns the statement description for sql. Returns nil if not found.
|
|
func (c *LRUCache) Get(key string) *pgconn.StatementDescription {
|
|
if el, ok := c.m[key]; ok {
|
|
c.l.MoveToFront(el)
|
|
return el.Value.(*pgconn.StatementDescription)
|
|
}
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
// Put stores sd in the cache. Put panics if sd.SQL is "". Put does nothing if sd.SQL already exists in the cache or
|
|
// sd.SQL has been invalidated and HandleInvalidated has not been called yet.
|
|
func (c *LRUCache) Put(sd *pgconn.StatementDescription) {
|
|
if sd.SQL == "" {
|
|
panic("cannot store statement description with empty SQL")
|
|
}
|
|
|
|
if _, present := c.m[sd.SQL]; present {
|
|
return
|
|
}
|
|
|
|
// The statement may have been invalidated but not yet handled. Do not readd it to the cache.
|
|
for _, invalidSD := range c.invalidStmts {
|
|
if invalidSD.SQL == sd.SQL {
|
|
return
|
|
}
|
|
}
|
|
|
|
if c.l.Len() == c.cap {
|
|
c.invalidateOldest()
|
|
}
|
|
|
|
el := c.l.PushFront(sd)
|
|
c.m[sd.SQL] = el
|
|
}
|
|
|
|
// Invalidate invalidates statement description identified by sql. Does nothing if not found.
|
|
func (c *LRUCache) Invalidate(sql string) {
|
|
if el, ok := c.m[sql]; ok {
|
|
delete(c.m, sql)
|
|
c.invalidStmts = append(c.invalidStmts, el.Value.(*pgconn.StatementDescription))
|
|
c.l.Remove(el)
|
|
}
|
|
}
|
|
|
|
// InvalidateAll invalidates all statement descriptions.
|
|
func (c *LRUCache) InvalidateAll() {
|
|
el := c.l.Front()
|
|
for el != nil {
|
|
c.invalidStmts = append(c.invalidStmts, el.Value.(*pgconn.StatementDescription))
|
|
el = el.Next()
|
|
}
|
|
|
|
c.m = make(map[string]*list.Element)
|
|
c.l = list.New()
|
|
}
|
|
|
|
// GetInvalidated returns a slice of all statement descriptions invalidated since the last call to RemoveInvalidated.
|
|
func (c *LRUCache) GetInvalidated() []*pgconn.StatementDescription {
|
|
return c.invalidStmts
|
|
}
|
|
|
|
// RemoveInvalidated removes all invalidated statement descriptions. No other calls to Cache must be made between a
|
|
// call to GetInvalidated and RemoveInvalidated or RemoveInvalidated may remove statement descriptions that were
|
|
// never seen by the call to GetInvalidated.
|
|
func (c *LRUCache) RemoveInvalidated() {
|
|
c.invalidStmts = nil
|
|
}
|
|
|
|
// Len returns the number of cached prepared statement descriptions.
|
|
func (c *LRUCache) Len() int {
|
|
return c.l.Len()
|
|
}
|
|
|
|
// Cap returns the maximum number of cached prepared statement descriptions.
|
|
func (c *LRUCache) Cap() int {
|
|
return c.cap
|
|
}
|
|
|
|
func (c *LRUCache) invalidateOldest() {
|
|
oldest := c.l.Back()
|
|
sd := oldest.Value.(*pgconn.StatementDescription)
|
|
c.invalidStmts = append(c.invalidStmts, sd)
|
|
delete(c.m, sd.SQL)
|
|
c.l.Remove(oldest)
|
|
}
|