Enum odbc_api::buffers::BufferKind

pub enum BufferKind {
    Binary {
        length: usize,
    },
    Text {
        max_str_len: usize,
    },
    WText {
        max_str_len: usize,
    },
    F64,
    F32,
    Date,
    Time,
    Timestamp,
    I8,
    I16,
    I32,
    I64,
    U8,
    Bit,
}

This class is used together with BufferDescription to specify the layout of buffers bound to ODBC cursors and statements.

Variants

Binary

Fields

length: usize

Maximum number of bytes per value.

Variable sized binary buffer, holding up to length bytes per value.

Text

Fields

max_str_len: usize

Maximum string length. Terminating zero is excluded, i.e. memory for it will be implicitly allocated if required.

Text buffer holding strings with binary length of up to max_str_len.

If choosing this based on the information in a DataType::Varchar column it is recommended to think about an upper bound. E.g. PostgreSQL may return a field size of several GiB for individual values if a column is specified as TEXT, or Microsoft SQL Server may return 0 for a column of type VARCHAR(max). In such situations, if values are truly that large, bulk fetching data is not recommended, but streaming individual fields one by one. Usually though, the actual cells of the table in the database contain much shorter value. The best thing todo is to adapt the database schema to better reflect the actual size of the values. Lacking control over the database schema, you can always choose a smaller buffer size than initializing the buffer in disagreement with the database schema.

WText

Fields

max_str_len: usize

Maximum string length. Terminating zero is excluded, i.e. memory for it will be implicitly allocated if required.

UTF-16 encoded text buffer holding strings with length of up to max_str_len. Length is in terms of 2-Byte characters.

F64

64 bit floating point

F32

32 bit floating point

Date

Describes a buffer holding crate::sys::Date values.

Time

Describes a buffer holding crate::sys::Time values.

Timestamp

Describes a buffer holding crate::sys::Timestamp values.

I8

Signed 8 Bit integer

I16

Signed 16 Bit integer

I32

Signed 32 Bit integer

I64

Signed 64 Bit integer

U8

Unsigned 8 Bit integer

Bit

Can either be zero or one

Implementations

impl BufferKind

pub fn from_data_type(data_type: DataType) -> Option<Self>

Describe a buffer which fits best the SQL Data Type.

use odbc_api::{DataType, buffers::BufferKind};

assert_eq!(BufferKind::from_data_type(DataType::Unknown), None);
assert_eq!(
    BufferKind::from_data_type(DataType::Numeric { precision: 2, scale: 0 }),
    Some(BufferKind::I8)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Numeric { precision: 9, scale: 0 }),
    Some(BufferKind::I32)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Numeric { precision: 18, scale: 0 }),
    Some(BufferKind::I64)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Numeric { precision: 20, scale: 5 }),
    Some(BufferKind::Text { max_str_len: 20 + 2 })
);
assert_eq!(
    BufferKind::from_data_type(DataType::Varchar { length: 42 }),
    Some(BufferKind::Text { max_str_len: 42 })
);
// We do not care about the encoding in the datasource. WVarchar is mapped to `Text`, too
// (instead of `WText`).
assert_eq!(
    BufferKind::from_data_type(DataType::WVarchar { length: 42 }),
    Some(BufferKind::Text { max_str_len: 42 })
);
assert_eq!(
    BufferKind::from_data_type(DataType::BigInt),
    Some(BufferKind::I64)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Integer),
    Some(BufferKind::I32)
);
assert_eq!(
    BufferKind::from_data_type(DataType::SmallInt),
    Some(BufferKind::I16)
);
assert_eq!(
    BufferKind::from_data_type(DataType::TinyInt),
    Some(BufferKind::I8)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Float { precision : 24 }),
    Some(BufferKind::F32)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Float { precision : 53 }),
    Some(BufferKind::F64)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Double),
    Some(BufferKind::F64)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Date),
    Some(BufferKind::Date)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Time { precision: 0 }),
    Some(BufferKind::Time)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Bit),
    Some(BufferKind::Bit)
);
assert_eq!(
    BufferKind::from_data_type(DataType::Time { precision: 3 }),
    Some(BufferKind::Text { max_str_len: 12 })
);
assert_eq!(
    BufferKind::from_data_type(DataType::Timestamp { precision: 3 }),
    Some(BufferKind::Timestamp)
);

Trait Implementations

impl Clone for BufferKind

fn clone(&self) -> BufferKind

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for BufferKind

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

Formats the value using the given formatter.

impl PartialEq<BufferKind> for BufferKind

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for BufferKind

impl Eq for BufferKind

impl StructuralEq for BufferKind

impl StructuralPartialEq for BufferKind