* Executing a query with a table or column alias exceeding 250 characters impacts the length of the MySQL field for the database name and column name, respectively, leading to garbage values being read at the end.

* Added TAP test

deps/mariadb-client-library/client_deprecate_eof.patch

@@ -170,7 +170,7 @@ index e475e25..1a04b2f 100644
 + */
 +int
 +unpack_field(const MYSQL *mysql, MA_MEM_ROOT *alloc, my_bool default_value,
-+    MYSQL_ROWS *row, MYSQL_FIELD *field)
++    MYSQL_ROWS *row, MYSQL_FIELD *field, ulong* field_length)
 +{
 +  unsigned int i, field_count = sizeof(rset_field_offsets) / sizeof(size_t) / 2;
 +  char *p = NULL;
@@ -187,7 +187,7 @@ index e475e25..1a04b2f 100644
 +    // Copy data in case of not empty
 +    else
 +    {
-+      uint length = (uint)(row->data[i+1] - row->data[i] - 1);
++      uint length = (uint)((field_length != NULL) ? field_length[i] : (row->data[i+1] - row->data[i] - 1));
 +      *(char **)(((char *)field) + rset_field_offsets[i*2]) =
 +        ma_strdup_root(alloc, (char *)row->data[i]);
 +      *(unsigned int *)(((char *)field) + rset_field_offsets[i*2+1]) =
@@ -314,7 +314,7 @@ index e475e25..1a04b2f 100644
 -    field->def_length= 0;
 -
 -    field->max_length= 0;
-+    if (unpack_field(mysql, alloc, default_value, row, field) != 0)
++    if (unpack_field(mysql, alloc, default_value, row, field, NULL) != 0)
 +      goto error;
    }
    if (field < result + fields)
@@ -440,7 +440,7 @@ index e475e25..1a04b2f 100644
 +    {
 +        if (mthd_my_read_one_row(mysql, m_field_count, m_rows.data, m_len) == -1)
 +          return NULL;
-+        if (unpack_field(mysql, mem_root, 0, &m_rows, m_fields++))
++        if (unpack_field(mysql, mem_root, 0, &m_rows, m_fields++, m_len))
 +          return NULL;
 +    }
 +    // read EOF packet in case of client not supporting 'CLIENT_DEPRECATE_EOF'

test/tap/tests/reg_test_4402-mysql_fields-t.cpp

@@ -0,0 +1,129 @@
+/**
+ * @file reg_test_4402-mysql-fields-t.cpp
+ * @brief This TAP test checks if the length of the column alias and table alias surpasses 250 characters, 
+ *		should not impact MySQL field name length (MySQL_FIELD::name_length) and the MySQL field database length (MySQL_FIELD::db_length)
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <string>
+#include <thread>
+#include "tap.h"
+#include "command_line.h"
+#include "utils.h" 
+
+#define MYSQL_QUERY__(mysql, query) \
+	do { \
+		if (mysql_query(mysql, query)) { \
+			fprintf(stderr, "File %s, line %d, Error: %s\n", \
+					__FILE__, __LINE__, mysql_error(mysql)); \
+			goto cleanup; \
+		} \
+	} while(0)
+
+CommandLine cl;
+
+std::string generate_random_string(size_t length) {
+	std::srand(static_cast<unsigned int>(std::time(nullptr)));
+	static const char characters[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+	static const int numCharacters = (sizeof(characters) - 1)/ sizeof(char);
+
+	std::string randomString;
+	randomString.reserve(length);
+
+	for (size_t i = 0; i < length; ++i) {
+		char randomChar = characters[std::rand() % numCharacters];
+		randomString.push_back(randomChar);
+	}
+
+	return randomString;
+}
+
+int main(int argc, char** argv) {
+
+	if (cl.getEnv()) {
+		diag("Failed to get the required environmental variables.");
+		return -1;
+	}
+
+	plan(256*2);
+
+	// 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();
+	}
+
+	MYSQL_QUERY__(proxysql, "DROP DATABASE IF EXISTS testdb");
+	MYSQL_QUERY__(proxysql, "CREATE DATABASE testdb");
+
+	diag("Creating echo_int function...");
+	MYSQL_QUERY__(proxysql, "CREATE FUNCTION testdb.echo_int(N INT) RETURNS INT DETERMINISTIC RETURN N;");
+	
+	diag("Creating dummy_table...");
+	MYSQL_QUERY__(proxysql, "CREATE TABLE testdb.dummy_table(data VARCHAR(10))");
+
+	// wait for replication
+	std::this_thread::sleep_for(std::chrono::seconds(2));
+	
+	// alias maximum length is 256.  
+	// https://dev.mysql.com/doc/refman/8.2/en/identifier-length.html
+	// https://mariadb.com/kb/en/identifier-names/#maximum-length
+	for (unsigned int length = 1; length <= 256; length++) {
+
+		// to check column alias issue:
+		{
+			const std::string& query = "SELECT testdb.echo_int(1) AS " + generate_random_string(length);
+			MYSQL_QUERY__(proxysql, query.c_str());
+
+			MYSQL_RES* res = mysql_use_result(proxysql);
+			if (!res) {
+				fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxysql));
+				return exit_status();
+			}
+
+			MYSQL_FIELD* field = mysql_fetch_fields(res);
+
+			ok(field->name_length == length, "name_length: '%u'. Expected length: '%u'", field->name_length, length);
+
+			if (res) {
+				mysql_free_result(res);
+				res = NULL;
+			}
+		}
+
+		// to check table alias issue:
+		{
+			const std::string& query = "SELECT data FROM testdb.dummy_table AS " + generate_random_string(length);
+			MYSQL_QUERY__(proxysql, query.c_str());
+
+			MYSQL_RES* res = mysql_use_result(proxysql);
+			if (!res) {
+				fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxysql));
+				return exit_status();
+			}
+
+			MYSQL_FIELD* field = mysql_fetch_fields(res);
+
+			ok(field->db_length == (sizeof("testdb")-1), "db_length: '%u'. Expected length: '%u'", 
+				field->db_length, (unsigned int)(sizeof("testdb")-1));
+
+			if (res) {
+				mysql_free_result(res);
+				res = NULL;
+			}
+		}
+	}
+cleanup:
+	mysql_query(proxysql, "DROP DATABASE IF EXISTS testdb");
+	mysql_close(proxysql);
+
+	return exit_status();
+}