Provide a log_level setting for auto_explain

Up to now the log level has been hardcoded at LOG. A new
auto_explain.log_level setting allows that to be modified.

Discussion: https://postgr.es/m/CAPPfruyZh+snR2AdmutrA0B_caj=yWZkLqxUTZYNjJCaQ_wKQg@mail.gmail.com

Tom Dunstan and Andrew Dunstan
Reviewed by Daniel Gustafsson

contrib/auto_explain/auto_explain.c

@@ -28,6 +28,7 @@ static bool auto_explain_log_buffers = false;
 static bool auto_explain_log_triggers = false;
 static bool auto_explain_log_timing = true;
 static int	auto_explain_log_format = EXPLAIN_FORMAT_TEXT;
+static int	auto_explain_log_level = LOG;
 static bool auto_explain_log_nested_statements = false;
 static double auto_explain_sample_rate = 1;
 
@@ -39,6 +40,20 @@ static const struct config_enum_entry format_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry loglevel_options[] = {
+	{"debug5", DEBUG5, false},
+	{"debug4", DEBUG4, false},
+	{"debug3", DEBUG3, false},
+	{"debug2", DEBUG2, false},
+	{"debug1", DEBUG1, false},
+	{"debug", DEBUG2, true},
+	{"info", INFO, false},
+	{"notice", NOTICE, false},
+	{"warning", WARNING, false},
+	{"log", LOG, false},
+	{NULL, 0, false}
+};
+
 /* Current nesting depth of ExecutorRun calls */
 static int	nesting_level = 0;
 
@@ -141,6 +156,18 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
+	DefineCustomEnumVariable("auto_explain.log_level",
+							 "Log level for the plan.",
+							 NULL,
+							 &auto_explain_log_level,
+							 LOG,
+							 loglevel_options,
+							 PGC_SUSET,
+							 0,
+							 NULL,
+							 NULL,
+							 NULL);
+
 	DefineCustomBoolVariable("auto_explain.log_nested_statements",
 							 "Log nested statements.",
 							 NULL,
@@ -353,7 +380,7 @@ explain_ExecutorEnd(QueryDesc *queryDesc)
 			 * reported.  This isn't ideal but trying to do it here would
 			 * often result in duplication.
 			 */
-			ereport(LOG,
+			ereport(auto_explain_log_level,
 					(errmsg("duration: %.3f ms  plan:\n%s",
 							msec, es->str->data),
 					 errhidestmt(true)));

doc/src/sgml/auto-explain.sgml

@@ -187,6 +187,27 @@ LOAD 'auto_explain';
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term>
+     <varname>auto_explain.log_level</varname> (<type>enum</type>)
+     <indexterm>
+      <primary><varname>auto_explain.log_level</> configuration parameter</primary>
+     </indexterm>
+    </term>
+    <listitem>
+     <para>
+      <varname>auto_explain.log_level</varname> selects the log level at which
+      auto_explain will log the query plan.
+      Valid values are <literal>DEBUG5</literal>, <literal>DEBUG4</literal>,
+      <literal>DEBUG3</literal>, <literal>DEBUG2</literal>,
+      <literal>DEBUG1</literal>, <literal>INFO</literal>,
+      <literal>NOTICE</literal>, <literal>WARNING</literal>,
+      and <literal>LOG</literal>. The default is <literal>LOG</literal>.
+      Only superusers can change this setting.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term>
      <varname>auto_explain.log_nested_statements</varname> (<type>boolean</type>)