ecpg: Refactor ecpg_log() to skip unnecessary calls to ECPGget_sqlca().

Previously, ecpg_log() always called ECPGget_sqlca() to retrieve sqlca,
even though it was only needed for debug logging. This commit updates
ecpg_log() to call ECPGget_sqlca() only when debug logging is enabled.

Author: Yuto Sasaki
Reviewed-by: Alvaro Herrera, Tom Lane, Fujii Masao
Discussion: https://postgr.es/m/TY2PR01MB3628A85689649BABC9A1C6C3C1782@TY2PR01MB3628.jpnprd01.prod.outlook.com

src/interfaces/ecpg/ecpglib/misc.c

@@ -232,10 +232,10 @@ void
 ecpg_log(const char *format,...)
 {
 	va_list		ap;
-	struct sqlca_t *sqlca = ECPGget_sqlca();
 	const char *intl_format;
 	int			bufsize;
 	char	   *fmt;
+	struct sqlca_t *sqlca;
 
 	/*
 	 * For performance reasons, inspect simple_debug without taking the mutex.
@@ -262,6 +262,8 @@ ecpg_log(const char *format,...)
 	else
 		snprintf(fmt, bufsize, "[%d]: %s", (int) getpid(), intl_format);
 
+	sqlca = ECPGget_sqlca();
+
 	pthread_mutex_lock(&debug_mutex);
 
 	/* Now that we hold the mutex, recheck simple_debug */