Fix InvalidCastException when summing double/float columns (#46)

[alex-clickhouse]

Summary

Fixes #46. Sum/SumAsync over a double or float column threw System.InvalidCastException before ever reaching ClickHouse:

System.InvalidCastException: Unable to cast object of type 'System.Int32' to type 'System.Double'.
   at ClickHouse.EntityFrameworkCore.Storage.Internal.Mapping.ClickHouseDoubleTypeMapping.GenerateNonNullSqlLiteral(Object value)

Root cause. EF Core wraps a top-level aggregate so the empty-result case returns 0, and supplies that fallback as a boxed Int32 carrying the column's Float64/Float32 type mapping. GenerateNonNullSqlLiteral unboxed it with a hard (double)/(float) cast, which throws for any runtime type other than the exact target.

While adding an end-to-end test I hit a second, related ClickHouse-specific issue: sum(Float32) widens to Float64, and the driver's GetFloat() refuses to downcast the returned Double — so summing a float column failed on the read path too.

Changes

• ClickHouseDoubleTypeMapping — Convert.ToDouble(...) instead of an unbox cast (NaN/±Infinity handling preserved).
• ClickHouseFloatTypeMapping — Convert.ToSingle(...) in the literal generator, plus a GetValue() + Convert.ToSingle() read path, mirroring ClickHouseIntegerTypeMapping (which already solves the same widening problem for COUNT → UInt64).
• The Double read path is intentionally left alone — Float64 is the widest float type ClickHouse aggregates return, so GetDouble() always works.

Type-system audit

I checked the whole type system for both bug classes:

• Literal hard-cast: only Double and Float were affected. Decimal/BigDecimal/BigInteger already use Convert.To*; integer mappings have no literal override; non-numeric mappings aren't Sum/Average targets.
• Aggregate read-path widening: a throwaway probe ran Sum/Average/Min/Max over every numeric type (small, boundary, and empty-result cases). With the fix in place all variants pass — integer mappings already handle their widening, and Decimal128 reads back fine within .NET decimal range.

Tests

• TypeMappingLiteralTests — boxed-Int32 literal for Double & Float (fail on the old cast).
• FloatSpecialValueTests — SumAsync over Float64/Float32 with matches and with a no-match predicate.
• AllTypesQueryTests — extended the Sum over Double gives InvalidCastException #46 guard across the adjacent types: Sum over Decimal (matches + empty), Sum over Int32 (widen-to-Int64 read) and Int64 (empty), and Average over Int32 (→ double).

All affected suites pass (85 tests); full solution builds with 0 errors. CHANGELOG.md and RELEASENOTES.md updated.

🤖 Generated with Claude Code

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[Copilot]

Pull request overview

Fixes ClickHouse EF Core type-mapping edge cases that caused Sum/SumAsync over double/float columns to throw InvalidCastException before or during result materialization, aligning literal generation and Float32 reading with EF Core’s boxed fallback behavior and ClickHouse aggregate widening.

Changes:

• Updated Float64/Float32 SQL literal generation to use Convert.ToDouble/ToSingle (avoids unboxing casts when EF supplies a boxed Int32 fallback 0).
• Updated Float32 materialization to read via DbDataReader.GetValue() and Convert.ToSingle() (handles sum(Float32) returning Float64).
• Added regression coverage across literal generation and end-to-end aggregate queries; documented fix in changelog/release notes.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/EFCore.ClickHouse.Tests/TypeMappingLiteralTests.cs	Adds regression tests ensuring boxed-Int32 fallback literals for Float32/Float64 don’t throw and don’t emit unnecessary casts.
test/EFCore.ClickHouse.Tests/FloatSpecialValueTests.cs	Adds end-to-end SumAsync coverage for Float64/Float32, including empty-result (0) cases.
test/EFCore.ClickHouse.Tests/AllTypesQueryTests.cs	Extends aggregate regression coverage to adjacent numeric types and widening behaviors (decimal, int32/int64, avg->double).
src/EFCore.ClickHouse/Storage/Internal/Mapping/ClickHouseFloatTypeMapping.cs	Fixes Float32 literal generation and materialization by converting instead of unboxing / typed reads.
src/EFCore.ClickHouse/Storage/Internal/Mapping/ClickHouseDoubleTypeMapping.cs	Fixes Float64 literal generation by converting instead of unboxing.
RELEASENOTES.md	Documents the user-visible bug fix for Sum/SumAsync over float/double.
CHANGELOG.md	Records the same fix details for v0.3.0 bug fixes.

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