Merge pull request #4724 from sysown/v2.7_reg_test_4723_query_cache_s…

…tores_empty_result

Fixed mysql-query_cache_stores_empty_result functionality

include/query_processor.h

@@ -164,7 +164,7 @@ class Query_Processor_Output {
 		mirror_flagOUT=-1;
 		next_query_flagIN=-1;
 		cache_ttl=-1;
-		cache_empty_result=1;
+		cache_empty_result=-1;
 		cache_timeout=-1;
 		reconnect=-1;
 		timeout=-1;

test/tap/tests/mysql-reg_test_4723_query_cache_stores_empty_result-t.cpp

@@ -0,0 +1,168 @@
+/**
+ * @file mysql-reg_test_4723_query_cache_stores_empty_result-t.cpp
+ * @brief This test verfies that 'mysql-query_cache_stores_empty_result' variable works as expected. 
+ *      Specifically, it ensures that when this variable is set to `0`, empty results (zero rows)
+ *      are not cached, and when set to `1`, they are cached.
+ *      The test verifies this behavior by comparing the metrics before and after query execution.
+ */
+
+#include <string>
+#include <sstream>
+
+#include "mysql.h"
+#include "command_line.h"
+#include "tap.h"
+#include "utils.h"
+
+CommandLine cl;
+
+std::map<std::string, int> getQueryCacheMetrics(MYSQL* proxy_admin) {
+    const char* query = "SELECT Variable_Name, Variable_Value FROM stats_mysql_global WHERE Variable_Name LIKE 'Query_Cache%';";
+    diag("Running: %s", query);
+
+    int query_res = mysql_query(proxy_admin, query);
+    if (query_res) {
+        BAIL_OUT("Query failed with error: %s", mysql_error(proxy_admin));
+        return {};
+    }
+
+    std::map<std::string, int> metrics{};
+    MYSQL_RES* res = mysql_store_result(proxy_admin);
+    if (!res) {
+        BAIL_OUT("Failed to store result: %s", mysql_error(proxy_admin));
+        return {};
+    }
+
+    MYSQL_ROW row;
+    while ((row = mysql_fetch_row(res))) {
+        metrics[row[0]] = atoi(row[1]);
+    }
+
+    mysql_free_result(res);
+    return metrics;
+}
+
+class TestMetrics {
+public:
+    std::map<std::string, int> before;
+    std::map<std::string, int> after;
+
+    void swap() {
+        before.swap(after);
+    }
+
+    template<class BinaryOp>
+    bool checkMetricDelta(const std::string& metric_name, int expected, BinaryOp op) {
+        if (before.find(metric_name) == before.end() || after.find(metric_name) == after.end()) {
+            diag("Metric '%s' not found in either before or after map.", metric_name.c_str());
+            return false;
+        }
+
+        int delta = after[metric_name] - before[metric_name];
+        bool result = op(std::max(0, delta), expected);
+
+        diag("Checking metric '%s': Expected delta %d, Actual delta %d", metric_name.c_str(), expected, delta);
+        ok(result, "Metric `%s` delta is correct. Expected '%d', got '%d'", metric_name.c_str(), expected, delta);
+        return result;
+    }
+};
+
+// Helper function for executing MySQL queries with error handling
+bool exec_query(MYSQL* conn, const char* query) {
+    diag("Running query: %s", query);
+    int query_res = mysql_query(conn, query);
+    if (query_res) {
+        diag("Query failed with error: %s", mysql_error(conn));
+        return false;
+    }
+    return true;
+}
+
+int main(int argc, char** argv) {
+    plan(10); // Total number of tests planned
+
+    if (cl.getEnv())
+        return exit_status();
+
+    // Initialize and connect to ProxySQL Admin
+    MYSQL* proxysql_admin = mysql_init(nullptr);
+    if (!proxysql_admin) {
+        BAIL_OUT("MySQL admin init failed.");
+    }
+
+    if (!mysql_real_connect(proxysql_admin, cl.admin_host, cl.admin_username, cl.admin_password, nullptr, cl.admin_port, nullptr, 0)) {
+        BAIL_OUT("Failed to connect to ProxySQL Admin: %s", mysql_error(proxysql_admin));
+    }
+
+    // Initialize and connect to ProxySQL Backend
+    MYSQL* proxysql_backend = mysql_init(nullptr);
+    if (!proxysql_backend) {
+        BAIL_OUT("MySQL backend init failed.");
+    }
+
+    if (!mysql_real_connect(proxysql_backend, cl.host, cl.username, cl.password, nullptr, cl.port, nullptr, 0)) {
+        BAIL_OUT("Failed to connect to ProxySQL Backend: %s", mysql_error(proxysql_backend));
+    }
+
+    // Setting up test environment
+    MYSQL_QUERY(proxysql_admin, "DELETE FROM mysql_query_rules");
+    MYSQL_QUERY(proxysql_admin, "INSERT INTO mysql_query_rules (rule_id,active,match_digest,cache_ttl) VALUES (2,1,'^SELECT',4000)");
+    MYSQL_QUERY(proxysql_admin, "LOAD MYSQL QUERY RULES TO RUNTIME");
+
+    // Disable query cache storing empty result
+    MYSQL_QUERY(proxysql_admin, "UPDATE global_variables SET variable_value=0 WHERE variable_name='mysql-query_cache_stores_empty_result'");
+    MYSQL_QUERY(proxysql_admin, "LOAD MYSQL VARIABLES TO RUNTIME");
+
+    TestMetrics metrics;
+
+    metrics.before = getQueryCacheMetrics(proxysql_admin);
+
+    // Execute the test query and check the result
+    if (exec_query(proxysql_backend, "SELECT 1 FROM DUAL WHERE 1!=1")) {
+        MYSQL_RES* res = mysql_store_result(proxysql_backend);
+        ok(res != nullptr, "Query executed successfully.");
+        mysql_free_result(res);
+    }
+    else {
+        ok(false, "Error executing query.");
+    }
+
+    // Fetch metrics after query execution
+    metrics.after = getQueryCacheMetrics(proxysql_admin);
+
+    metrics.checkMetricDelta("Query_Cache_Memory_bytes", 0, std::equal_to<int>());
+    metrics.checkMetricDelta("Query_Cache_count_SET", 0, std::equal_to<int>());
+    metrics.checkMetricDelta("Query_Cache_bytes_IN", 0, std::equal_to<int>());
+    metrics.checkMetricDelta("Query_Cache_Entries", 0, std::equal_to<int>());
+
+    // Swap the before and after metrics for the next phase
+    metrics.swap();
+
+    // Enable query cache storing empty result
+    MYSQL_QUERY(proxysql_admin, "UPDATE global_variables SET variable_value=1 WHERE variable_name='mysql-query_cache_stores_empty_result'");
+    MYSQL_QUERY(proxysql_admin, "LOAD MYSQL VARIABLES TO RUNTIME");
+
+    // Execute the same query again and check the result
+    if (exec_query(proxysql_backend, "SELECT 1 FROM DUAL WHERE 1!=1")) {
+        MYSQL_RES* res = mysql_store_result(proxysql_backend);
+        ok(res != nullptr, "Query executed successfully.");
+        mysql_free_result(res);
+    }
+    else {
+        ok(false, "Error executing query.");
+    }
+
+    // Fetch metrics again and check for expected changes
+    metrics.after = getQueryCacheMetrics(proxysql_admin);
+
+    metrics.checkMetricDelta("Query_Cache_Memory_bytes", 1, std::greater<int>());
+    metrics.checkMetricDelta("Query_Cache_count_SET", 1, std::equal_to<int>());
+    metrics.checkMetricDelta("Query_Cache_bytes_IN", 1, std::greater<int>());
+    metrics.checkMetricDelta("Query_Cache_Entries", 1, std::equal_to<int>());
+
+    // Close the connections
+    mysql_close(proxysql_backend);
+    mysql_close(proxysql_admin);
+
+    return exit_status();
+}