apache-arrow/schema.mjs

Apache Arrow columnar in-memory format

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.
import { MetadataVersion } from './enum.mjs';
import { DataType } from './type.mjs';
export class Schema {
    constructor(fields = [], metadata, dictionaries, metadataVersion = MetadataVersion.V5) {
        this.fields = (fields || []);
        this.metadata = metadata || new Map();
        if (!dictionaries) {
            dictionaries = generateDictionaryMap(this.fields);
        }
        this.dictionaries = dictionaries;
        this.metadataVersion = metadataVersion;
    }
    get [Symbol.toStringTag]() { return 'Schema'; }
    get names() { return this.fields.map((f) => f.name); }
    toString() {
        return `Schema<{ ${this.fields.map((f, i) => `${i}: ${f}`).join(', ')} }>`;
    }
    /**
     * Construct a new Schema containing only specified fields.
     *
     * @param fieldNames Names of fields to keep.
     * @returns A new Schema of fields matching the specified names.
     */
    select(fieldNames) {
        const names = new Set(fieldNames);
        const fields = this.fields.filter((f) => names.has(f.name));
        return new Schema(fields, this.metadata);
    }
    /**
     * Construct a new Schema containing only fields at the specified indices.
     *
     * @param fieldIndices Indices of fields to keep.
     * @returns A new Schema of fields at the specified indices.
     */
    selectAt(fieldIndices) {
        const fields = fieldIndices.map((i) => this.fields[i]).filter(Boolean);
        return new Schema(fields, this.metadata);
    }
    assign(...args) {
        const other = (args[0] instanceof Schema
            ? args[0]
            : Array.isArray(args[0])
                ? new Schema(args[0])
                : new Schema(args));
        const curFields = [...this.fields];
        const metadata = mergeMaps(mergeMaps(new Map(), this.metadata), other.metadata);
        const newFields = other.fields.filter((f2) => {
            const i = curFields.findIndex((f) => f.name === f2.name);
            return ~i ? (curFields[i] = f2.clone({
                metadata: mergeMaps(mergeMaps(new Map(), curFields[i].metadata), f2.metadata)
            })) && false : true;
        });
        const newDictionaries = generateDictionaryMap(newFields, new Map());
        return new Schema([...curFields, ...newFields], metadata, new Map([...this.dictionaries, ...newDictionaries]));
    }
}
// Add these here so they're picked up by the externs creator
// in the build, and closure-compiler doesn't minify them away
Schema.prototype.fields = null;
Schema.prototype.metadata = null;
Schema.prototype.dictionaries = null;
export class Field {
    /** @nocollapse */
    static new(...args) {
        let [name, type, nullable, metadata] = args;
        if (args[0] && typeof args[0] === 'object') {
            ({ name } = args[0]);
            (type === undefined) && (type = args[0].type);
            (nullable === undefined) && (nullable = args[0].nullable);
            (metadata === undefined) && (metadata = args[0].metadata);
        }
        return new Field(`${name}`, type, nullable, metadata);
    }
    constructor(name, type, nullable = false, metadata) {
        this.name = name;
        this.type = type;
        this.nullable = nullable;
        this.metadata = metadata || new Map();
    }
    get typeId() { return this.type.typeId; }
    get [Symbol.toStringTag]() { return 'Field'; }
    toString() { return `${this.name}: ${this.type}`; }
    clone(...args) {
        let [name, type, nullable, metadata] = args;
        (!args[0] || typeof args[0] !== 'object')
            ? ([name = this.name, type = this.type, nullable = this.nullable, metadata = this.metadata] = args)
            : ({ name = this.name, type = this.type, nullable = this.nullable, metadata = this.metadata } = args[0]);
        return Field.new(name, type, nullable, metadata);
    }
}
// Add these here so they're picked up by the externs creator
// in the build, and closure-compiler doesn't minify them away
Field.prototype.type = null;
Field.prototype.name = null;
Field.prototype.nullable = null;
Field.prototype.metadata = null;
/** @ignore */
function mergeMaps(m1, m2) {
    return new Map([...(m1 || new Map()), ...(m2 || new Map())]);
}
/** @ignore */
function generateDictionaryMap(fields, dictionaries = new Map()) {
    for (let i = -1, n = fields.length; ++i < n;) {
        const field = fields[i];
        const type = field.type;
        if (DataType.isDictionary(type)) {
            if (!dictionaries.has(type.id)) {
                dictionaries.set(type.id, type.dictionary);
            }
            else if (dictionaries.get(type.id) !== type.dictionary) {
                throw new Error(`Cannot create Schema containing two different dictionaries with the same Id`);
            }
        }
        if (type.children && type.children.length > 0) {
            generateDictionaryMap(type.children, dictionaries);
        }
    }
    return dictionaries;
}

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