[Enhancement] files() type promotion

[rickif]

Why I'm doing:

The files() would merge file schemas. The current rule of merging is too simple.

What I'm doing:

This PR makes some improvements to the files type promotion, including the following changes:

1. promote decimal types to bigger decimal type
2. promote string types to bigger string type
3. promote float type and integer type to double type
4. promote different complex types to vachar.
   Fixes [schema auto-detection merge] when query file table function the data file has different decimal type of parquet format, error #38992

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
• This is a backport pr

Bugfix cherry-pick branch check:

• I have checked the version labels which the pr will be auto-backported to the target branch
  • 3.2
  • 3.1
  • 3.0
  • 2.5

[starrocks-cr]

The most risky bug in this code is:
incorrect or missing handling for type conflicts between integer and float types in the promote_types method

You can modify the code like this:

    static TypeDescriptor promote_types(const TypeDescriptor& type1, const TypeDescriptor& type2) {
        DCHECK(type1 != type2);
        if (type1.is_integer_type() && type2.is_integer_type()) {
            // promote integer type. Larger enum values mean larger value ranges.
            auto tp = type1.type > type2.type ? type1.type : type2.type;
            return TypeDescriptor::from_logical_type(tp);
        } else if ((type1.is_float_type() && type2.is_integer_type()) || (type1.is_integer_type() && type2.is_float_type())) {
            // if one is float and other is integer, promote to double
            return TypeDescriptor::from_logical_type(TYPE_DOUBLE);
        } else if (type1.is_float_type() && type2.is_float_type()) {
            // promote all float to double.
            return TypeDescriptor::from_logical_type(TYPE_DOUBLE);
        } else if (type1.is_decimal_type() && type2.is_decimal_type()) {
            // decimal v3 only
            auto tp = type1.type > type2.type ? type1.type : type2.type;
            if (tp > TYPE_DECIMAL128) tp = TYPE_DECIMAL128;
            if (tp < TYPE_DECIMAL32) tp = TYPE_DECIMAL32;
            auto precision = type1.precision > type2.precision ? type1.precision : type2.precision;
            if (precision > MAX_PRECISION) precision = MAX_PRECISION;
            auto scale = type1.scale > type2.scale ? type1.scale : type2.scale;
            if (scale > MAX_SCALE) scale = MAX_SCALE;
            return TypeDescriptor::create_decimalv3_type(tp, precision, scale);
        } else if (type1.type == TYPE_VARCHAR && type2.type == TYPE_VARCHAR) {
            auto len = type1.len > type2.len ? type1.len : type2.len;
            return TypeDescriptor::create_varchar_type(len);
        } else if (type1.type == TYPE_CHAR && type2.type == TYPE_CHAR) {
            auto len = type1.len > type2.len ? type1.len : type2.len;
            return TypeDescriptor::create_char_type(len);
        } else if (type1.type == TYPE_VARBINARY && type2.type == TYPE_VARBINARY) {
            auto len = type1.len > type2.len ? type1.len : type2.len;
            return TypeDescriptor::create_varbinary_type(len);
        }
        // treat other conflicted types as varchar.
        return TypeDescriptor::create_varchar_type(TypeDescriptor::MAX_VARCHAR_LENGTH);
    }

This modification aims to address the risk by adding a case to handle the scenario where one type is an integer and the other is a float, promoting the result to double, thus preventing potential loss of precision or incorrect type promotion.

[dirtysalt]

Does this comment help you ?

[rickif]

@dirtysalt Yeah. I've changed the PR according to the comment.

[dirtysalt]

use MAX_CHAR_LENGTH better?

[rickif]

@Mergifyio rebase

[mergify]

rebase

✅ Branch has been successfully rebased

[rickif]

@Mergifyio rebase

[mergify]

rebase

✅ Branch has been successfully rebased

[github-actions]

[FE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[BE Incremental Coverage Report]

✅ pass : 38 / 38 (100.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	be/src/exec/file_scanner.cpp	4	4	100.00%	[]
🔵	be/src/runtime/types.h	5	5	100.00%	[]
🔵	be/src/runtime/types.cpp	29	29	100.00%	[]

[github-actions]

@Mergifyio backport branch-3.2

[mergify]

backport branch-3.2

✅ Backports have been created

• #41782 [Enhancement] files() type promotion (backport #40959) has been created for branch branch-3.2