Rename PreparedStatementDescription to StatementDescription

PreparedStatementDescription was too long. It also no longer entirely
represents its purpose now that it is also intended for use with
described statements.

pgconn.go

@@ -517,15 +517,16 @@ func (ct CommandTag) String() string {
 	return string(ct)
 }
 
-type PreparedStatementDescription struct {
+type StatementDescription struct {
 	Name      string
 	SQL       string
 	ParamOIDs []uint32
 	Fields    []pgproto3.FieldDescription
 }
 
-// Prepare creates a prepared statement.
-func (pgConn *PgConn) Prepare(ctx context.Context, name, sql string, paramOIDs []uint32) (*PreparedStatementDescription, error) {
+// Prepare creates a prepared statement. If the name is empty, the anonymous prepared statement will be used. This
+// allows Prepare to also to describe statements without creating a server-side prepared statement.
+func (pgConn *PgConn) Prepare(ctx context.Context, name, sql string, paramOIDs []uint32) (*StatementDescription, error) {
 	if err := pgConn.lock(); err != nil {
 		return nil, linkErrors(err, ErrNoBytesSent)
 	}
@@ -553,7 +554,7 @@ func (pgConn *PgConn) Prepare(ctx context.Context, name, sql string, paramOIDs [
 		return nil, linkErrors(ctx.Err(), err)
 	}
 
-	psd := &PreparedStatementDescription{Name: name, SQL: sql}
+	psd := &StatementDescription{Name: name, SQL: sql}
 
 	var parseErr error
 

stmtcache/lru.go

@@ -40,10 +40,10 @@ func NewLRU(conn *pgconn.PgConn, mode int, cap int) *LRU {
 }
 
 // Get returns the prepared statement description for sql preparing or describing the sql on the server as needed.
-func (c *LRU) Get(ctx context.Context, sql string) (*pgconn.PreparedStatementDescription, error) {
+func (c *LRU) Get(ctx context.Context, sql string) (*pgconn.StatementDescription, error) {
 	if el, ok := c.m[sql]; ok {
 		c.l.MoveToFront(el)
-		return el.Value.(*pgconn.PreparedStatementDescription), nil
+		return el.Value.(*pgconn.StatementDescription), nil
 	}
 
 	if c.l.Len() == c.cap {
@@ -91,7 +91,7 @@ func (c *LRU) Mode() int {
 	return c.mode
 }
 
-func (c *LRU) prepare(ctx context.Context, sql string) (*pgconn.PreparedStatementDescription, error) {
+func (c *LRU) prepare(ctx context.Context, sql string) (*pgconn.StatementDescription, error) {
 	var name string
 	if c.mode == ModePrepare {
 		name = fmt.Sprintf("%s_%d", c.psNamePrefix, c.prepareCount)
@@ -105,7 +105,7 @@ func (c *LRU) removeOldest(ctx context.Context) error {
 	oldest := c.l.Back()
 	c.l.Remove(oldest)
 	if c.mode == ModePrepare {
-		return c.conn.Exec(ctx, fmt.Sprintf("deallocate %s", oldest.Value.(*pgconn.PreparedStatementDescription).Name)).Close()
+		return c.conn.Exec(ctx, fmt.Sprintf("deallocate %s", oldest.Value.(*pgconn.StatementDescription).Name)).Close()
 	}
 	return nil
 }

stmtcache/stmtcache.go

@@ -15,7 +15,7 @@ const (
 // 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.PreparedStatementDescription, error)
+	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