fix type inconsistency #45

Job	Run time
Check cargo fmt	40s
cargo check	5m 29s
build with wasm-pack	2m 24s
cargo test (macos)	9m 24s
cargo test (macos-aarch64)	11m 58s
Verify MSRV (Min Supported Rust Version)	6m 59s
Verify Vendored Code	51s
cargo test (win64)	43m 58s
cargo examples (amd64)	13m 28s
cargo test hash collisions (amd64)	14m 21s
cargo doc	4m 14s
check Cargo.toml formatting	2m 54s
clippy	5m 48s
cargo test (amd64)	9m 42s
cargo test datafusion-cli (amd64)	4m 0s
cargo test doc (amd64)	14m 59s
Run sqllogictest with Postgres runner	3m 35s
cargo test pyarrow (amd64)	2m 49s
verify benchmark results (amd64)	12m 22s
check configs.md is up-to-date	2m 52s
	2h 52m 47s

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