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57 lines
2.0 KiB
Rust
57 lines
2.0 KiB
Rust
use crate::database::Database;
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use either::Either;
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use std::convert::identity;
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/// Provides extended information on a statement.
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///
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/// Returned from [`Executor::describe`].
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///
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/// The query macros (e.g., `query!`, `query_as!`, etc.) use the information here to validate
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/// output and parameter types; and, generate an anonymous record.
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#[derive(Debug)]
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#[cfg_attr(feature = "offline", derive(serde::Serialize, serde::Deserialize))]
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#[cfg_attr(
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feature = "offline",
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serde(bound(
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serialize = "DB::TypeInfo: serde::Serialize, DB::Column: serde::Serialize",
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deserialize = "DB::TypeInfo: serde::de::DeserializeOwned, DB::Column: serde::de::DeserializeOwned",
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))
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)]
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#[doc(hidden)]
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pub struct Describe<DB: Database> {
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pub(crate) columns: Vec<DB::Column>,
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pub(crate) parameters: Option<Either<Vec<DB::TypeInfo>, usize>>,
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pub(crate) nullable: Vec<Option<bool>>,
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}
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impl<DB: Database> Describe<DB> {
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/// Gets all columns in this statement.
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pub fn columns(&self) -> &[DB::Column] {
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&self.columns
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}
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/// Gets the column information at `index`.
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///
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/// Panics if `index` is out of bounds.
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pub fn column(&self, index: usize) -> &DB::Column {
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&self.columns[index]
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}
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/// Gets the available information for parameters in this statement.
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///
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/// Some drivers may return more or less than others. As an example, **PostgreSQL** will
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/// return `Some(Either::Left(_))` with a full list of type information for each parameter.
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/// However, **MSSQL** will return `None` as there is no information available.
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pub fn parameters(&self) -> Option<Either<&[DB::TypeInfo], usize>> {
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self.parameters.as_ref().map(|p| match p {
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Either::Left(params) => Either::Left(&**params),
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Either::Right(count) => Either::Right(*count),
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})
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}
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/// Gets whether a column may be `NULL`, if this information is available.
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pub fn nullable(&self, column: usize) -> Option<bool> {
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self.nullable.get(column).copied().and_then(identity)
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}
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}
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