mirror of
https://github.com/superseriousbusiness/gotosocial.git
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109 lines
2.7 KiB
Go
109 lines
2.7 KiB
Go
package stmtcache
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import (
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"container/list"
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"github.com/jackc/pgx/v5/pgconn"
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)
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// LRUCache implements Cache with a Least Recently Used (LRU) cache.
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type LRUCache struct {
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cap int
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m map[string]*list.Element
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l *list.List
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invalidStmts []*pgconn.StatementDescription
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}
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// NewLRUCache creates a new LRUCache. cap is the maximum size of the cache.
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func NewLRUCache(cap int) *LRUCache {
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return &LRUCache{
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cap: cap,
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m: make(map[string]*list.Element),
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l: list.New(),
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}
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}
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// Get returns the statement description for sql. Returns nil if not found.
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func (c *LRUCache) Get(key string) *pgconn.StatementDescription {
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if el, ok := c.m[key]; ok {
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c.l.MoveToFront(el)
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return el.Value.(*pgconn.StatementDescription)
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}
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return nil
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}
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// Put stores sd in the cache. Put panics if sd.SQL is "". Put does nothing if sd.SQL already exists in the cache or
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// sd.SQL has been invalidated and HandleInvalidated has not been called yet.
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func (c *LRUCache) Put(sd *pgconn.StatementDescription) {
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if sd.SQL == "" {
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panic("cannot store statement description with empty SQL")
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}
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if _, present := c.m[sd.SQL]; present {
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return
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}
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// The statement may have been invalidated but not yet handled. Do not readd it to the cache.
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for _, invalidSD := range c.invalidStmts {
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if invalidSD.SQL == sd.SQL {
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return
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}
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}
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if c.l.Len() == c.cap {
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c.invalidateOldest()
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}
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el := c.l.PushFront(sd)
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c.m[sd.SQL] = el
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}
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// Invalidate invalidates statement description identified by sql. Does nothing if not found.
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func (c *LRUCache) Invalidate(sql string) {
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if el, ok := c.m[sql]; ok {
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delete(c.m, sql)
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c.invalidStmts = append(c.invalidStmts, el.Value.(*pgconn.StatementDescription))
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c.l.Remove(el)
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}
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}
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// InvalidateAll invalidates all statement descriptions.
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func (c *LRUCache) InvalidateAll() {
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el := c.l.Front()
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for el != nil {
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c.invalidStmts = append(c.invalidStmts, el.Value.(*pgconn.StatementDescription))
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el = el.Next()
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}
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c.m = make(map[string]*list.Element)
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c.l = list.New()
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}
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// HandleInvalidated returns a slice of all statement descriptions invalidated since the last call to HandleInvalidated.
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// Typically, the caller will then deallocate them.
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func (c *LRUCache) HandleInvalidated() []*pgconn.StatementDescription {
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invalidStmts := c.invalidStmts
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c.invalidStmts = nil
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return invalidStmts
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}
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// Len returns the number of cached prepared statement descriptions.
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func (c *LRUCache) Len() int {
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return c.l.Len()
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}
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// Cap returns the maximum number of cached prepared statement descriptions.
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func (c *LRUCache) Cap() int {
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return c.cap
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}
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func (c *LRUCache) invalidateOldest() {
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oldest := c.l.Back()
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sd := oldest.Value.(*pgconn.StatementDescription)
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c.invalidStmts = append(c.invalidStmts, sd)
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delete(c.m, sd.SQL)
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c.l.Remove(oldest)
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}
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