executor: load data statement shoule not be prepared (#21188)

[ti-srebot]

cherry-pick #21188 to release-3.0

---

What problem does this PR solve?

tidb throw unexpected error while execute load data statement in prepare statement

Problem Summary:

The current error is：
‘Load data: previous load data option isn't closed normal’。
expected error is：
‘This command is not supported in the prepared statement protocol yet‘

What is changed and how it works?

What's Changed:

add a logic, if there is load data in prepare statement, return error 'ErrUnsupportedPs'

How it Works:
add a logic, if there is load data in prepare statement, return error 'ErrUnsupportedPs'

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

1. execute
   load data local infile 't1.txt' into table t1 fields terminated by '|' ignore 1 lines
2. below log will show in the log file.

[2020/11/22 21:31:11.349 +08:00] [INFO] [conn.go:801] ["command dispatched failed"] [conn=2199023255557] [connInfo="id:2199023255557, addr:127.0.0.1:56357 status:10, collation:utf8_general_ci, user:root"] [command=Prepare] [status="inTxn:0, autocommit:1"] [sql="load data local infile 't1.txt' into table t1 fields terminated by '|' ignore 1 lines"] [txn_mode=OPTIMISTIC] [err="[executor:1295]This command is not supported in the prepared statement protocol yet"]

• No code

Side effects

• Performance regression
  • Consumes more CPU
  • Consumes more MEM
• Breaking backward compatibility

Release note

• Raise an error when preparing the load data statement.

[ti-srebot]

/run-all-tests

[ti-srebot]

@ti-srebot you're already a collaborator in bot's repo.

[7yyo]

/build

[jackysp]

errors.toml should be deleted.

[jackysp]

LGTM

[lysu]

LGTM

[jackysp]

/approve

[jackysp]

/merge

[ti-srebot]

/run-all-tests