ChDriver.
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The scalar/fixed-width column type codec table, plus the primitive wire readers it's built on.
Covers ClickHouse's fixed-width integer and float types, String,
Bool, DateTime, Enum8/Enum16, UUID, IPv4, and IPv6. Adding
a new scalar type is a one-line addition to column_codec/1.
UUID values decode to their standard hyphenated text form. IPv4/IPv6
decode to dotted-quad / colon-hex text. DateTime decodes to a UTC
DateTime.t(). Date decodes to a Date.t(). Bool decodes to a
boolean.
DateTime64(P) is parameterized by its precision, so it can't be a
fixed entry in column_codec/1's table -- it's dispatched from
ChDriver.Protocol.NativeBlock through decode_datetime64/2 instead.
Summary
Functions
Looks up the fixed-width/string codec for a scalar ClickHouse type name.
Returns {:fixed, byte_size, unpack_fun}, :string, or :unsupported.
Decodes a DateTime64(P) tick count of precision decimal places into
a UTC DateTime.t().
Reads num_rows fixed-width byte_size-byte chunks from binary,
running each through unpack (e.g. fn <<v::unsigned-little-32>> -> v end). Returns {:ok, values, rest} or {:incomplete, binary} if fewer
than num_rows * byte_size bytes are available.
Reads remaining ClickHouse String values (varint length prefix +
bytes) from binary. Returns {:ok, values, rest} or {:incomplete, binary}.
Functions
Looks up the fixed-width/string codec for a scalar ClickHouse type name.
Returns {:fixed, byte_size, unpack_fun}, :string, or :unsupported.
Decodes a DateTime64(P) tick count of precision decimal places into
a UTC DateTime.t().
Unlike plain DateTime's unsigned whole-second UInt32, DateTime64
is a signed little-endian Int64 count of 10^-P-second ticks since
the Unix epoch, so it covers pre-epoch instants (negative ticks) as
well as sub-second resolution.
Elixir's DateTime only carries microsecond resolution, so a precision
above 6 (e.g. DateTime64(9)'s nanoseconds) is truncated -- toward
negative infinity via Integer.floor_div/2, so that a pre-epoch value's
microsecond remainder stays non-negative and the reconstructed
DateTime is still the correct instant rather than one second off. The
reported microsecond precision is capped at 6 for the same reason,
while a lower precision is preserved as-is (a DateTime64(3) value
loads back as {ms * 1000, 3}, not silently widened to 6).
Reads num_rows fixed-width byte_size-byte chunks from binary,
running each through unpack (e.g. fn <<v::unsigned-little-32>> -> v end). Returns {:ok, values, rest} or {:incomplete, binary} if fewer
than num_rows * byte_size bytes are available.
Reads remaining ClickHouse String values (varint length prefix +
bytes) from binary. Returns {:ok, values, rest} or {:incomplete, binary}.