Decode internal "char" type (OID 18) natively#168
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@Dev-iL Could you please check lint stages? |
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Yeah, forgot to enable hooks locally after cloning. Will fix shortly... |
Fixes psqlpy-python#165. Any query touching PostgreSQL system catalogs (pg_type, pg_class, pg_attribute, pg_proc, ...) raised RustToPyValueMappingError because the internal "char" type — distinct from character(n)/BPCHAR — had no native decoder and fell through to other_postgres_bytes_to_py. Add an InternalChar(u8) wrapper next to the existing InternalUuid / InnerDecimal / InnerInterval helpers and wire it into postgres_bytes_to_py via two new match arms (Type::CHAR, Type::CHAR_ARRAY). The byte is read through tokio-postgres' i8 FromSql impl, cast back to u8, and mapped to a one-character Python str through char::from(u8) — i.e. Unicode code points 0..=255 (Latin-1 round-trip), matching psycopg2/psycopg3. The custom_decoders dispatch is intentionally unchanged: it stays keyed by column name per the existing documented contract. Tests: - python/tests/test_value_converter.py: * test_char_internal_type_pg_type_reproduction — exact snippet from psqlpy-python#165 * test_char_internal_type_byte_spectrum — reachable ASCII bytes 0x20, 0x41, 0x61, 0x7E plus NULL (SQL chr() rejects NUL and re-encodes >=0x80 as multi-byte UTF-8) * test_char_internal_type_array — "char"[] decoded to list[str] - src/value_converter/models/internal_char.rs: * from_sql_round_trips_full_byte_range — full 0..=255 byte mapping the SQL test cannot reach * accepts_only_char_type — type guard rejects TEXT/VARCHAR/BPCHAR
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Description
Adds a native decoder for PostgreSQL's internal
"char"type (OID 18) and its array variant. A newInternalChar(u8)wrapper sits alongside the existingInternalUuid/InnerDecimal/InnerIntervalhelpers; two new arms inpostgres_bytes_to_py(Type::CHAR,Type::CHAR_ARRAY) decode the single wire byte to a one-character Pythonstrviachar::from(u8)— Unicode code points 0..=255, Latin-1 round-trip, matching psycopg2/psycopg3.custom_decoderskeying is intentionally unchanged (still column-name-keyed, lowercase, per the existing documented contract).Motivation and Context
Fixes #165.
Querying any column of the internal
"char"type — distinct fromcharacter(n)/BPCHAR — raisedRustToPyValueMappingError: Cannot convert _char into Python type, please look at the custom_decoders functionality.The type had no native decoder and fell through toother_postgres_bytes_to_py. The error message pointed atcustom_decoders, but that path is keyed by column name, not type, so for users hitting this throughpg_type/pg_class/pg_attribute/pg_proc(where"char"columns are pervasive —pg_typealone has five) it offered no workable escape.How has this been tested?
cargo build --releasecargo clippy --all-targets -- -D warnings— cleancargo test --release internal_char— 2 passed (full 0..=255 byte round-trip +accepts()type guard rejects TEXT / VARCHAR / BPCHAR)pytest python/tests/test_value_converter.py— 163 passed, including three new tests:test_char_internal_type_pg_type_reproduction— the exact failing snippet from the issuetest_char_internal_type_byte_spectrum— round-trips bytes0x20 / 0x41 / 0x61 / 0x7Eplus NULL through a temp"char"column (SQLchr()rejects NUL and re-encodes>= 0x80as multi-byte UTF-8 of which only the first byte is stored, so the full 0..=255 range is exercised by the Rust unit test instead)test_char_internal_type_array— decodesARRAY['a'::"char", 'b'::"char", 'c'::"char"]to["a", "b", "c"]RustToPyValueMappingError: Cannot convert _char into Python typeerror; with the fix in place, they pass.Tested against PostgreSQL 14 (psqlpy's lowest supported major version) on Linux / Python 3.12.
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