Struct Cost 

pub struct Cost {
    pub source: Option<String>,
    pub uncompressed: Option<u64>,
    pub codec: Option<String>,
    pub row_groups: Option<usize>,
    pub partitions: Option<Partitions>,
    pub tables: Option<usize>,
    pub opens_one: bool,
    pub ipc_stream: bool,
}

What pressing Enter on a dataset will actually cost.

rows, cols and size say what a dataset is. None of them say what reading it will do, and the difference is large: 200 MB of zstd-compressed Parquet is two gigabytes in memory, and two gigabytes on a hotel-wifi NFS mount is a different afternoon than two gigabytes on tmpfs.

Every field here comes from something datui already reads — the mount table, and the same Parquet footer that yields the row count. Nothing here costs an extra byte of the dataset itself.

Fields

source: Option<String>

Filesystem or URL scheme: nfs4, ext4, tmpfs, fuse.sshfs, s3.

uncompressed: Option<u64>

Bytes once decompressed — what this will occupy, as against what it occupies on disk.

codec: Option<String>

Compression codec, as the file itself names it.

row_groups: Option<usize>

Row groups. One enormous row group cannot be read in parallel or skipped through; a thousand tiny ones cost more in overhead than they save.

partitions: Option<Partitions>

Partition layout, for a hive dataset.

tables: Option<usize>

Tables of its own, for a file of tables: one opens, several are listed.

opens_one: bool

Whether a file of several tables opens one of them (a workbook’s first sheet), so Enter opens it and → lists them, rather than Enter listing them.

ipc_stream: bool

An Arrow file that is an IPC stream, which is converted before it is scanned, rather than an IPC file, which is scanned where it is. From its first bytes.

Trait Implementations

impl Clone for Cost

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Cost

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Cost

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Cost

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for Cost

impl PartialEq for Cost

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for Cost

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Cost