Ethan Pailes
a885de9c94
This patch adds a new StatementErrored method to the stmtcache. This routine MUST be called by users of the cache whenever the execution of a statement results in an error. This will allow the cache to make an intelligent decision about whether or not the statement needs to be purged from the cache.
61 lines
2.1 KiB
Go
61 lines
2.1 KiB
Go
// Package stmtcache is a cache that can be used to implement lazy prepared statements.
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package stmtcache
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import (
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"context"
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"github.com/jackc/pgconn"
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)
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const (
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ModePrepare = iota // Cache should prepare named statements.
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ModeDescribe // Cache should prepare the anonymous prepared statement to only fetch the description of the statement.
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)
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// Cache prepares and caches prepared statement descriptions.
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type Cache interface {
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// Get returns the prepared statement description for sql preparing or describing the sql on the server as needed.
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Get(ctx context.Context, sql string) (*pgconn.StatementDescription, error)
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// Clear removes all entries in the cache. Any prepared statements will be deallocated from the PostgreSQL session.
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Clear(ctx context.Context) error
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// StatementErrored informs the cache that the given statement resulted in an error when it
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// was last used against the database. In some cases, this will cause the cache to flush
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// the statement from the cache. It will only do so when the underlying `*pgconn.PgConn`
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// is not currently in a transaction. If the connection is in the middle of a transaction,
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// the bad statement will instead be flushed during the next call to Get that occurrs outside
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// of a transaction.
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StatementErrored(ctx context.Context, sql string, err error) error
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// Len returns the number of cached prepared statement descriptions.
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Len() int
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// Cap returns the maximum number of cached prepared statement descriptions.
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Cap() int
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// Mode returns the mode of the cache (ModePrepare or ModeDescribe)
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Mode() int
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}
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// New returns the preferred cache implementation for mode and cap. mode is either ModePrepare or ModeDescribe. cap is
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// the maximum size of the cache.
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func New(conn *pgconn.PgConn, mode int, cap int) Cache {
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mustBeValidMode(mode)
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mustBeValidCap(cap)
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return NewLRU(conn, mode, cap)
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}
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func mustBeValidMode(mode int) {
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if mode != ModePrepare && mode != ModeDescribe {
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panic("mode must be ModePrepare or ModeDescribe")
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}
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}
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func mustBeValidCap(cap int) {
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if cap < 1 {
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panic("cache must have cap of >= 1")
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}
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}
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