(you don't have to strictly follow this form)

It seems that CH doesn't support  `FORMAT CustomSeparated` with http request
https://github.com/ClickHouse/ClickHouse/issues/12744#issuecomment-663738562

When I make a request with `format_custom_field_delimiter='^'`, I got an error
```
Code: 49, e.displayText() = DB::Exception: There is no checkpoint (version 20.1.2.4 (official build)) 
```
Bash script:
```
#!/bin/bash

find . -type f -name 'j.log' | while read f; do
  curl "http://localhost:8123
/?query=INSERT%20INTO%20mydb%20FORMAT%20CustomSeparated%20SETTINGS%20format_custom_escaping_rule%3D%27CSV%27%2C%20format_custom_field_delimiter%20%3D%20%27%5E%27" --data-binary "@${f}"
done
```
But all is OK, when I do it with client:
```
cat j.log |clickhouse-client  -q "INSERT into mydb FORMAT CustomSeparated SETTINGS format_custom_escaping_rule='CSV', format_custom_field_delimiter = '^'"
```


**How to reproduce**
* Which ClickHouse server version to use
 version 20.13.1.1 and github build `commit 6e34a0b71efc0e5af1cfb05b77a5e7b2568a2e49`
* Which interface to use, if matters
* Non-default settings, if any
* `CREATE TABLE` statements for all tables involved
```
CREATE TABLE mydb
(
	datetime  String,
	d1 String,
	d2 String
)
engine=MergeTree()
ORDER BY d1
SETTINGS index_granularity = 8192;
```
* Sample data for all these tables, use [clickhouse-obfuscator](https://github.com/ClickHouse/ClickHouse/blob/master/programs/obfuscator/Obfuscator.cpp#L42-L80) if necessary

j.log:
```
2021-Jan^d1^d2
```

* Queries to run that lead to unexpected result

**Expected behavior**
A clear and concise description of what you expected to happen.

**Error message and/or stacktrace**
If applicable, add screenshots to help explain your problem.

**Additional context**
Add any other context about the problem here.

{
            bool is_trivial_insert_select = false;
            if (settings.optimize_trivial_insert_select)
            {
                const auto & select_query = query.select->as<ASTSelectWithUnionQuery &>();
                const auto & selects = select_query.list_of_selects->children;
                const auto & union_modes = select_query.list_of_modes;
                
                is_trivial_insert_select
                    = std::all_of(
                          union_modes.begin(),
                          union_modes.end(),
                          [](const ASTSelectWithUnionQuery::Mode & mode) { return mode == ASTSelectWithUnionQuery::Mode::ALL; })
                    && std::all_of(selects.begin(), selects.end(), [](const ASTPtr & select) { return isTrivialSelect(select); });
            }
            if (is_trivial_insert_select)
            {
                /** When doing trivial INSERT INTO ... SELECT ... FROM table,
                  * don't need to process SELECT with more than max_insert_threads
                  * and it's reasonable to set block size for SELECT to the desired block size for INSERT
                  * to avoid unnecessary squashing.
                  */
                Settings new_settings = context.getSettings();
                new_settings.max_threads = std::max<UInt64>(1, settings.max_insert_threads);
                if (settings.min_insert_block_size_rows)
                    new_settings.max_block_size = settings.min_insert_block_size_rows;
                Context new_context = context;
                new_context.setSettings(new_settings);
                InterpreterSelectWithUnionQuery interpreter_select{
                    query.select, new_context, SelectQueryOptions(QueryProcessingStage::Complete, 1)};