Fixed crash on frequently querying stats_mysql_query_digest* tables

lib/Query_Processor.cpp

@@ -1154,9 +1154,6 @@ unsigned long long Query_Processor::purge_query_digests(bool async_purge, bool p
 
 unsigned long long Query_Processor::purge_query_digests_async(char **msg) {
 	unsigned long long ret = 0;
-	pthread_rwlock_wrlock(&digest_rwlock);
-
-
 	umap_query_digest digest_umap_aux;
 	umap_query_digest_text digest_text_umap_aux;
 	pthread_rwlock_wrlock(&digest_rwlock);
@@ -1399,7 +1396,7 @@ std::pair<SQLite3_result *, int> Query_Processor::get_query_digests_v2(const boo
 			digest_umap_aux.insert(element);
 		}
 	}
-	digest_text_umap.insert(digest_text_umap_aux.begin(), digest_text_umap_aux.end());
+	digest_text_umap_aux.insert(digest_text_umap_aux_2.begin(), digest_text_umap_aux_2.end());
 	digest_umap_aux_2.clear();
 	digest_text_umap_aux_2.clear();
 
@@ -1409,7 +1406,6 @@ std::pair<SQLite3_result *, int> Query_Processor::get_query_digests_v2(const boo
 	// content of the auxiliary maps.
 	pthread_rwlock_wrlock(&digest_rwlock);
 	digest_umap_aux.swap(digest_umap);
-	digest_text_umap_aux.swap(digest_text_umap);
 	for (const auto& element : digest_umap_aux) {
 		uint64_t digest = element.first;
 		QP_query_digest_stats *qds = (QP_query_digest_stats *)element.second;

test/tap/tests/reg_test_4399-stats_mysql_query_digest-t.cpp

@@ -0,0 +1,93 @@
+/**
+ * @file reg_test_4399-stats_mysql_query_digest-t.cpp
+ * @brief This test verifies stability of ProxySQL by checking if it remains operational when 
+ *		stats_mysql_query_digest table is queried frequently while actively serving traffic.
+ */
+
+#include <stdio.h>
+#include <future>
+#include <thread>
+#include "mysql.h"
+#include "mysqld_error.h"
+#include "tap.h"
+#include "command_line.h"
+#include "utils.h" 
+
+CommandLine cl;
+
+const unsigned int QUERY_COUNT = 1000;
+
+int main(int argc, char** argv) {
+	if (cl.getEnv()) {
+		diag("Failed to get the required environmental variables.");
+		return -1;
+	}
+
+	plan(2);
+
+	// Initialize Admin connection
+	MYSQL* proxysql_admin = mysql_init(NULL);
+	if (!proxysql_admin) {
+		fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxysql_admin));
+		return -1;
+	}
+	// Connnect to ProxySQL Admin
+	if (!mysql_real_connect(proxysql_admin, cl.host, cl.admin_username, cl.admin_password, NULL, cl.admin_port, NULL, 0)) {
+		fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxysql_admin));
+		return -1;
+	}
+
+	MYSQL_QUERY(proxysql_admin, "SET mysql-query_digests='true'");
+	MYSQL_QUERY(proxysql_admin, "SET mysql-query_digests_keep_comment='true'");
+	MYSQL_QUERY(proxysql_admin, "SET mysql-query_digests_normalize_digest_text='true'");
+	MYSQL_QUERY(proxysql_admin, "SET mysql-query_digests_max_digest_length=2048");
+	MYSQL_QUERY(proxysql_admin, "LOAD MYSQL VARIABLES TO RUNTIME");
+
+	// clearing previously stored digests
+	MYSQL_QUERY(proxysql_admin, "SELECT COUNT(*) FROM stats_mysql_query_digest_reset");
+	mysql_free_result(mysql_store_result(proxysql_admin));
+
+	// Initialize ProxySQL connection
+	MYSQL* proxysql = mysql_init(NULL);
+	if (!proxysql) {
+		fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxysql));
+		return -1;
+	}
+
+	// Connect to ProxySQL
+	if (!mysql_real_connect(proxysql, cl.host, cl.username, cl.password, NULL, cl.port, NULL, 0)) {
+		fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxysql));
+		return exit_status();
+	}
+
+	auto handle = std::async(std::launch::async, [&]() -> int {
+			char query[128]{};
+			diag("Generating simulated traffic...");
+			for (unsigned int i=0; i < QUERY_COUNT; i++) {
+				sprintf(query, "DO /*#%d#*/ %d", i, i);
+				MYSQL_QUERY(proxysql, query);
+				std::this_thread::sleep_for(std::chrono::milliseconds(1));
+			}
+			return EXIT_SUCCESS; 
+		}
+	);
+
+	bool result = true;
+	diag("Querying stats_mysql_query_digest table...");
+	for (unsigned int i=0; i < QUERY_COUNT; i++) {
+		if (mysql_query(proxysql_admin, "SELECT COUNT(*) FROM stats_mysql_query_digest")) {
+			fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxysql_admin));
+			result = false;
+			break;
+		}
+		mysql_free_result(mysql_store_result(proxysql_admin));
+		std::this_thread::sleep_for(std::chrono::milliseconds(1));
+	}
+	ok(result == true, "All queries on stats_mysql_query_digest table were executed successfully");
+	ok(handle.get() == EXIT_SUCCESS, "Successfully ran a set of dummy queries to simulate traffic");
+
+	mysql_close(proxysql);
+	mysql_close(proxysql_admin);
+
+	return exit_status();
+}