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// Package stmtcache is a cache that can be used to implement lazy prepared statements.
package stmtcache
import (
"context"
"github.com/jackc/pgconn"
)
const (
ModePrepare = iota // Cache should prepare named statements.
ModeDescribe // Cache should prepare the anonymous prepared statement to only fetch the description of the statement.
)
// Cache prepares and caches prepared statement descriptions.
type Cache interface {
// Get returns the prepared statement description for sql preparing or describing the sql on the server as needed.
Get(ctx context.Context, sql string) (*pgconn.StatementDescription, error)
// Clear removes all entries in the cache. Any prepared statements will be deallocated from the PostgreSQL session.
Clear(ctx context.Context) error
// StatementErrored informs the cache that the given statement resulted in an error when it
// was last used against the database. In some cases, this will cause the cache to maer that
// statement as bad. The bad statement will instead be flushed during the next call to Get
// that occurs outside of a failed transaction.
StatementErrored(sql string, err error)
// Len returns the number of cached prepared statement descriptions.
Len() int
// Cap returns the maximum number of cached prepared statement descriptions.
Cap() int
// Mode returns the mode of the cache (ModePrepare or ModeDescribe)
Mode() int
}
// New returns the preferred cache implementation for mode and cap. mode is either ModePrepare or ModeDescribe. cap is
// the maximum size of the cache.
func New(conn *pgconn.PgConn, mode int, cap int) Cache {
mustBeValidMode(mode)
mustBeValidCap(cap)
return NewLRU(conn, mode, cap)
}
func mustBeValidMode(mode int) {
if mode != ModePrepare && mode != ModeDescribe {
panic("mode must be ModePrepare or ModeDescribe")
}
}
func mustBeValidCap(cap int) {
if cap < 1 {
panic("cache must have cap of >= 1")
}
}
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