@dpkit/table/build/table/denormalize.js

Data Package implementation in TypeScript.

import { col, lit } from "nodejs-polars";
import { stringifyField } from "../field/index.js";
import { getPolarsSchema } from "../schema/index.js";
const HEAD_ROWS = 100;
export async function denormalizeTable(table, schema, options) {
    const head = await table.head(HEAD_ROWS).collect();
    const polarsSchema = getPolarsSchema(head.schema);
    return table.select(Object.values(denormalizeFields(schema, polarsSchema, options)));
}
export function denormalizeFields(schema, polarsSchema, options) {
    const { nativeTypes } = options ?? {};
    const exprs = {};
    for (const field of schema.fields) {
        const polarsField = polarsSchema.fields.find(f => f.name === field.name);
        let expr = lit(null).alias(field.name);
        if (polarsField) {
            expr = col(polarsField.name).alias(field.name);
            if (!nativeTypes?.includes(field.type ?? "any")) {
                const missingValues = field.missingValues ?? schema.missingValues;
                const mergedField = { ...field, missingValues };
                expr = stringifyField(mergedField, expr);
            }
        }
        exprs[field.name] = expr;
    }
    return exprs;
}
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