feat: add PostgresRowSequence.getColumns() to get column metadata #577
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This commit implements `PostgresRowSequence.getColumns()` to enable users to retrieve column metadata of their query results. Discussion: vapor#576
Just my two cents — I'm happy to adjust based on the maintainer's feedback. :) |
| /// The column name. | ||
| public let name: String | ||
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| /// If the field can be identified as a column of a specific table, the object ID of the table; otherwise zero. | ||
| public let tableOID: Int32 | ||
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| /// If the field can be identified as a column of a specific table, the attribute number of the column; otherwise zero. | ||
| public let columnAttributeNumber: Int16 | ||
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| /// The object ID of the field's data type. | ||
| public let dataType: PostgresDataType | ||
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| /// The data type size (see pg_type.typlen). Note that negative values denote variable-width types. | ||
| public let dataTypeSize: Int16 | ||
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| /// The type modifier (see pg_attribute.atttypmod). The meaning of the modifier is type-specific. | ||
| public let dataTypeModifier: Int32 | ||
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| /// The format being used for the field. Currently will be text or binary. In a RowDescription returned | ||
| /// from the statement variant of Describe, the format code is not yet known and will always be text. | ||
| public let format: PostgresFormat |
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can we back this with a RowDescription.Column please. Instead of let properties please lets use computed properties.
Example:
public var name: String {
self.underlying.name
}
| /// Get the column information of the query results. | ||
| public func getColumns() -> [PostgresColumn] { | ||
| self.columns.map { column in | ||
| PostgresColumn( | ||
| name: column.name, | ||
| tableOID: column.tableOID, | ||
| columnAttributeNumber: column.columnAttributeNumber, | ||
| dataType: column.dataType, | ||
| dataTypeSize: column.dataTypeSize, | ||
| dataTypeModifier: column.dataTypeModifier, | ||
| format: column.format | ||
| ) | ||
| } | ||
| } |
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This is an O(n) call. Where n equals the number of columns. Do we need a returned Array? Can we return a custom PostgresColumns struct that wraps the existing [RowDescription.Column] structure?
Example:
struct PostgresColumns: Sequence {
typealias Element == PostgresColumn
var underlying: [RowDescription.Column]
func makeIterator() -> Iterator {
Iterator(underlying: self.underlying.makeIterator)
}
struct Iterator: IteratorProtocol {
var underlying: [RowDescription.Column].Iterator
func next() -> PostgresColumn {
self.underlying.next()
}
}
}
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If we do the above we can just add a get only property:
var columns: PostgresColumns {
PostgresColumns(underlying: self.columns)
}
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Also thanks for pushing on this @SteveLauC. My apologies for not coming back to you sooner. |
This commit implements
PostgresRowSequence.getColumns()to enable users to retrieve column metadata of their query results.Discussion: #576
Closes #576