fix(query): fix variant map access filter

[b41sh]

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Summary

Fix conflicting precedence of MapAccess and And, since the value of both of them is 20, we can't get the correct syntax tree when parsing the following SQL.

SELECT * FROM test WHERE id = 1 and labels:email = 'abc@test.com';

When performing data filtering, if the data types of the comparison are different, we will perform an implicit data type cast. For JSON values, some cast can't be successful, such as casting a string to a number or casting null to a string. Since the cast target type is not nullable, the following error will occur.

mysql> SELECT * FROM test WHERE labels:email = 'abc@test.com';
ERROR 1105 (HY000): Code: 1010, displayText = Cast error happens in casting from Variant to String (while in processor thread 0).

In order to solve this problem, we allow the cast target type to be nullable and mark the null value rows as deleted after the comparison operation.

Fixes #6590

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1 Ignored Deployment

Name	Status	Preview	Updated
databend	⬜️ Ignored (Inspect)		Jul 15, 2022 at 10:11AM (UTC)

[BohuTANG]

We can add more documents about the variant map with this patch @soyeric128