are used by mssql ensure these cached properties are initialized to prevent queries for the mariadb or mysql version during the queryset evaluation are used by mssql ensure these cached properties are initialized to prevent queries for the mariadb or mysql version during the queryset evaluation
import json
import unittest
import xml.etree.ElementTree

from django.db import NotSupportedError, connection, transaction
from django.db.models import Count
from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
from django.test.utils import CaptureQueriesContext

from .models import Tag


@skipUnlessDBFeature("supports_explaining_query_execution")
class ExplainTests(TestCase):
    def test_basic(self):
        querysets = [
            Tag.objects.filter(name="test"),
            Tag.objects.filter(name="test").select_related("parent"),
            Tag.objects.filter(name="test").prefetch_related("children"),
            Tag.objects.filter(name="test").annotate(Count("children")),
            Tag.objects.filter(name="test").values_list("name"),
            Tag.objects.order_by().union(Tag.objects.order_by().filter(name="test")),
        ]
        if connection.features.has_select_for_update:
            querysets.append(Tag.objects.select_for_update().filter(name="test"))
        supported_formats = connection.features.supported_explain_formats
        all_formats = (
            (None,)
            + tuple(supported_formats)
            + tuple(f.lower() for f in supported_formats)
        )
        for idx, queryset in enumerate(querysets):
            for format in all_formats:
                with self.subTest(format=format, queryset=idx):
                    with self.assertNumQueries(1) as captured_queries:
                        result = queryset.explain(format=format)
                        self.assertTrue(
                            captured_queries[0]["sql"].startswith(
                                connection.ops.explain_prefix
                            )
                        )
                        self.assertIsInstance(result, str)
                        self.assertTrue(result)
                        if not format:
                            continue
                        if format.lower() == "xml":
                            try:
                                xml.etree.ElementTree.fromstring(result)
                            except xml.etree.ElementTree.ParseError as e:
                                self.fail(
                                    f"QuerySet.explain() result is not valid XML: {e}"
                                )
                        elif format.lower() == "json":
                            try:
                                json.loads(result)
                            except json.JSONDecodeError as e:
                                self.fail(
                                    f"QuerySet.explain() result is not valid JSON: {e}"
                                )

    def test_unknown_options(self):
        with self.assertRaisesMessage(ValueError, "Unknown options: TEST, TEST2"):
            Tag.objects.explain(**{"TEST": 1, "TEST2": 1})

    def test_unknown_format(self):
        msg = "DOES NOT EXIST is not a recognized format."
        if connection.features.supported_explain_formats:
            msg += " Allowed formats: %s" % ", ".join(
                sorted(connection.features.supported_explain_formats)
            )
        else:
            msg += f" {connection.display_name} does not support any formats."
        with self.assertRaisesMessage(ValueError, msg):
            Tag.objects.explain(format="does not exist")

    @unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific")
    def test_postgres_options(self):
        qs = Tag.objects.filter(name="test")
        test_options = [
            {"COSTS": False, "BUFFERS": True, "ANALYZE": True},
            {"costs": False, "buffers": True, "analyze": True},
            {"verbose": True, "timing": True, "analyze": True},
            {"verbose": False, "timing": False, "analyze": True},
            {"summary": True},
            {"settings": True},
            {"analyze": True, "wal": True},
        ]
        if connection.features.is_postgresql_16:
            test_options.append({"generic_plan": True})
        for options in test_options:
            with self.subTest(**options), transaction.atomic():
                with CaptureQueriesContext(connection) as captured_queries:
                    qs.explain(format="text", **options)
                self.assertEqual(len(captured_queries), 1)
                for name, value in options.items():
                    option = "{} {}".format(name.upper(), "true" if value else "false")
                    self.assertIn(option, captured_queries[0]["sql"])

    def test_option_sql_injection(self):
        qs = Tag.objects.filter(name="test")
        options = {"SUMMARY true) SELECT 1; --": True}
        msg = "Invalid option name: 'SUMMARY true) SELECT 1; --'"
        with self.assertRaisesMessage(ValueError, msg):
            qs.explain(**options)

    def test_invalid_option_names(self):
        qs = Tag.objects.filter(name="test")
        tests = [
            'opt"ion',
            "o'ption",
            "op`tion",
            "opti on",
            "option--",
            "optio\tn",
            "o\nption",
            "option;",
            "你 好",
            
            "option[",
            "option]",
        ]
        for invalid_option in tests:
            with self.subTest(invalid_option):
                msg = f"Invalid option name: {invalid_option!r}"
                with self.assertRaisesMessage(ValueError, msg):
                    qs.explain(**{invalid_option: True})

    @unittest.skipUnless(connection.vendor == "mysql", "MySQL specific")
    def test_mysql_text_to_traditional(self):
        
        
        connection.features.supported_explain_formats
        with CaptureQueriesContext(connection) as captured_queries:
            Tag.objects.filter(name="test").explain(format="text")
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("FORMAT=TRADITIONAL", captured_queries[0]["sql"])

    @unittest.skipUnless(
        connection.vendor == "mysql", "MariaDB and MySQL >= 8.0.18 specific."
    )
    def test_mysql_analyze(self):
        qs = Tag.objects.filter(name="test")
        with CaptureQueriesContext(connection) as captured_queries:
            qs.explain(analyze=True)
        self.assertEqual(len(captured_queries), 1)
        prefix = "ANALYZE " if connection.mysql_is_mariadb else "EXPLAIN ANALYZE "
        self.assertTrue(captured_queries[0]["sql"].startswith(prefix))
        with CaptureQueriesContext(connection) as captured_queries:
            qs.explain(analyze=True, format="JSON")
        self.assertEqual(len(captured_queries), 1)
        if connection.mysql_is_mariadb:
            self.assertIn("FORMAT=JSON", captured_queries[0]["sql"])
        else:
            self.assertNotIn("FORMAT=JSON", captured_queries[0]["sql"])


@skipIfDBFeature("supports_explaining_query_execution")
class ExplainUnsupportedTests(TestCase):
    def test_message(self):
        msg = "This backend does not support explaining query execution."
        with self.assertRaisesMessage(NotSupportedError, msg):
            Tag.objects.filter(name="test").explain()