type ClauseType = 
  | "data"
  | "joins"
  | "expressions"
  | "filter"
  | "aggregation"
  | "breakout"
  | "order-by"
  | "limit";

function previewQuery(query: Query, stageIndex: number, clauseType: ClauseType, clauseIndex: number | null): Query

const query = {
  "source-table": 1,
  "joins": [join1, join2],
  "expressions: { ... },
  "filter": ["and, filter1, filter],
  "aggregation": [aggregation1, aggregation2],
  "breakout": [breakout1, breakout2],
  ...
}

previewQuery(query, 0, "data") =>
{
  "source-table": 1,
}

previewQuery(query, 0, "joins") =>
{
  "source-table": 1,
  "joins": [join1, join2]
}

previewQuery(query, 0, "joins", 0) =>
{
  "source-table": 1,
  "joins": [join1]
}

previewQuery(query, 0, "expressions") =>
{
  "source-table": 1,
  "joins": [join1, join2],
  "expressions": { ... }
}