[rudycelekli]

Why

Trino's client protocol writes most numbers as JSON numbers, but it writes decimal as a string. In JsonEncodingUtils, a SqlDecimal goes through generator.writeString(decimalValue.toString()) (source). The Trino engine passed data through untouched. A money column, or any SUM/AVG over one, reached the model as "1234.50", while COUNT(*) in the same row was the number 7.

The other HTTP engines already restore these values by column type: Databricks and Snowflake through coerce, ClickHouse through its cell. As the coerce comment notes, the model does arithmetic differently on "42" and 42. A Trino, Starburst, Iceberg or Hive catalog was the one place where amounts stayed quoted.

What changes

Column now also reads the type each column already carries. After the pages are collected, cells in a decimal(p,s) column go through coerce("DECIMAL", …), the same conversion Databricks and Snowflake decimals get. Nulls stay null, and other types are untouched.

How it was checked

• A new wiremock test, a_decimal_reads_as_a_number, returns varchar(5), decimal(12,2) and bigint columns, including a null decimal. It expects {"region":"east","total":1234.5,"orders":7}.
• cargo test -p utopia-server --bins query_engine: 73 passed.
• With the fix reverted, the test fails with left: ["{\"region\":\"east\",\"total\":\"1234.50\",\"orders\":7}", …].
• cargo fmt --all --check and cargo clippy -p utopia-server --all-targets -- -D warnings pass.

Before review

• Every commit is signed off (git commit -s)
• cargo fmt --all --check, cargo clippy and cargo test pass for the touched crate

Requested ADR follow-up

Updated ADR 0018 as requested in review. This appended revision changes documentation only; Rust and Cargo files are byte-for-byte unchanged from the prior public head. cargo fmt --all --check and git diff --check pass. No new Rust test run or live-cluster acceptance is claimed for this revision. Final-head CI remains required.

Merge after #1413, as requested; the ADR retains that exact-value dependency.

[WaylandYang]

Correct. Please add Trino decimals to ADR 0018's fourth-gate paragraph. We'll merge this after #1413 so long decimals keep their digits.

[WaylandYang]

Thanks. After #1412 landed this conflicted in ADR 0018, so I merged dev into the branch, kept both sentences, and reworded yours to the present tense now that the long-decimal guard from #1413 goes in first. Approving and merging.