SelectStage

Keep a projection (columns) or compute one (exprs) — exactly one.

opOp (string)required

Constant value: select

exprs object

anyOf

• object[]
• null

Array [

nameName (string)required

Output column name

exprExpr (string)required

Polars-SQL expression, e.g. 'qty * unit_price'

]

columns object

anyOf

• string[]
• null

Array [

string

]

SelectStage

{
  "op": "select",
  "exprs": [
    {
      "name": "string",
      "expr": "string"
    }
  ],
  "columns": [
    "string"
  ]
}