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combine_docs_chain.ts
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combine_docs_chain.ts
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import { Document } from "@langchain/core/documents";
import { ChainValues } from "@langchain/core/utils/types";
import { CallbackManagerForChainRun } from "@langchain/core/callbacks/manager";
import { BasePromptTemplate, PromptTemplate } from "@langchain/core/prompts";
import type {
SerializedStuffDocumentsChain,
SerializedMapReduceDocumentsChain,
SerializedRefineDocumentsChain,
} from "./serde.js";
import { BaseChain, ChainInputs } from "./base.js";
import { LLMChain } from "./llm_chain.js";
/**
* Interface for the input properties of the StuffDocumentsChain class.
*/
export interface StuffDocumentsChainInput extends ChainInputs {
/** LLM Wrapper to use after formatting documents */
llmChain: LLMChain;
inputKey?: string;
/** Variable name in the LLM chain to put the documents in */
documentVariableName?: string;
}
/**
* Chain that combines documents by stuffing into context.
* @augments BaseChain
* @augments StuffDocumentsChainInput
*/
export class StuffDocumentsChain
extends BaseChain
implements StuffDocumentsChainInput
{
static lc_name() {
return "StuffDocumentsChain";
}
llmChain: LLMChain;
inputKey = "input_documents";
documentVariableName = "context";
get inputKeys() {
return [this.inputKey, ...this.llmChain.inputKeys].filter(
(key) => key !== this.documentVariableName
);
}
get outputKeys() {
return this.llmChain.outputKeys;
}
constructor(fields: StuffDocumentsChainInput) {
super(fields);
this.llmChain = fields.llmChain;
this.documentVariableName =
fields.documentVariableName ?? this.documentVariableName;
this.inputKey = fields.inputKey ?? this.inputKey;
}
/** @ignore */
_prepInputs(values: ChainValues): ChainValues {
if (!(this.inputKey in values)) {
throw new Error(`Document key ${this.inputKey} not found.`);
}
const { [this.inputKey]: docs, ...rest } = values;
const texts = (docs as Document[]).map(({ pageContent }) => pageContent);
const text = texts.join("\n\n");
return {
...rest,
[this.documentVariableName]: text,
};
}
/** @ignore */
async _call(
values: ChainValues,
runManager?: CallbackManagerForChainRun
): Promise<ChainValues> {
const result = await this.llmChain.call(
this._prepInputs(values),
runManager?.getChild("combine_documents")
);
return result;
}
_chainType() {
return "stuff_documents_chain" as const;
}
static async deserialize(data: SerializedStuffDocumentsChain) {
if (!data.llm_chain) {
throw new Error("Missing llm_chain");
}
return new StuffDocumentsChain({
llmChain: await LLMChain.deserialize(data.llm_chain),
});
}
serialize(): SerializedStuffDocumentsChain {
return {
_type: this._chainType(),
llm_chain: this.llmChain.serialize(),
};
}
}
/**
* Interface for the input properties of the MapReduceDocumentsChain
* class.
*/
export interface MapReduceDocumentsChainInput extends StuffDocumentsChainInput {
/** The maximum number of tokens before requiring to do the reduction */
maxTokens?: number;
/** The maximum number of iterations to run through the map */
maxIterations?: number;
/** Ensures that the map step is taken regardless of max tokens */
ensureMapStep?: boolean;
/** Chain to use to combine results of applying llm_chain to documents. */
combineDocumentChain: StuffDocumentsChain;
/** Return the results of the map steps in the output. */
returnIntermediateSteps?: boolean;
}
/**
* Combine documents by mapping a chain over them, then combining results.
* @augments BaseChain
* @augments StuffDocumentsChainInput
*/
export class MapReduceDocumentsChain
extends BaseChain
implements MapReduceDocumentsChainInput
{
static lc_name() {
return "MapReduceDocumentsChain";
}
llmChain: LLMChain;
inputKey = "input_documents";
documentVariableName = "context";
returnIntermediateSteps = false;
get inputKeys() {
return [this.inputKey, ...this.combineDocumentChain.inputKeys];
}
get outputKeys() {
return this.combineDocumentChain.outputKeys;
}
maxTokens = 3000;
maxIterations = 10;
ensureMapStep = false;
combineDocumentChain: StuffDocumentsChain;
constructor(fields: MapReduceDocumentsChainInput) {
super(fields);
this.llmChain = fields.llmChain;
this.combineDocumentChain = fields.combineDocumentChain;
this.documentVariableName =
fields.documentVariableName ?? this.documentVariableName;
this.ensureMapStep = fields.ensureMapStep ?? this.ensureMapStep;
this.inputKey = fields.inputKey ?? this.inputKey;
this.maxTokens = fields.maxTokens ?? this.maxTokens;
this.maxIterations = fields.maxIterations ?? this.maxIterations;
this.returnIntermediateSteps = fields.returnIntermediateSteps ?? false;
}
/** @ignore */
async _call(
values: ChainValues,
runManager?: CallbackManagerForChainRun
): Promise<ChainValues> {
if (!(this.inputKey in values)) {
throw new Error(`Document key ${this.inputKey} not found.`);
}
const { [this.inputKey]: docs, ...rest } = values;
let currentDocs = docs as Document[];
let intermediateSteps: string[] = [];
// For each iteration, we'll use the `llmChain` to get a new result
for (let i = 0; i < this.maxIterations; i += 1) {
const inputs = currentDocs.map((d) => ({
[this.documentVariableName]: d.pageContent,
...rest,
}));
const canSkipMapStep = i !== 0 || !this.ensureMapStep;
if (canSkipMapStep) {
// Calculate the total tokens required in the input
const formatted =
await this.combineDocumentChain.llmChain.prompt.format(
this.combineDocumentChain._prepInputs({
[this.combineDocumentChain.inputKey]: currentDocs,
...rest,
})
);
const length = await this.combineDocumentChain.llmChain._getNumTokens(
formatted
);
const withinTokenLimit = length < this.maxTokens;
// If we can skip the map step, and we're within the token limit, we don't
// need to run the map step, so just break out of the loop.
if (withinTokenLimit) {
break;
}
}
const results = await this.llmChain.apply(
inputs,
// If we have a runManager, then we need to create a child for each input
// so that we can track the progress of each input.
runManager
? Array.from({ length: inputs.length }, (_, i) =>
runManager.getChild(`map_${i + 1}`)
)
: undefined
);
const { outputKey } = this.llmChain;
// If the flag is set, then concat that to the intermediate steps
if (this.returnIntermediateSteps) {
intermediateSteps = intermediateSteps.concat(
results.map((r) => r[outputKey])
);
}
currentDocs = results.map((r) => ({
pageContent: r[outputKey],
metadata: {},
}));
}
// Now, with the final result of all the inputs from the `llmChain`, we can
// run the `combineDocumentChain` over them.
const newInputs = {
[this.combineDocumentChain.inputKey]: currentDocs,
...rest,
};
const result = await this.combineDocumentChain.call(
newInputs,
runManager?.getChild("combine_documents")
);
// Return the intermediate steps results if the flag is set
if (this.returnIntermediateSteps) {
return { ...result, intermediateSteps };
}
return result;
}
_chainType() {
return "map_reduce_documents_chain" as const;
}
static async deserialize(data: SerializedMapReduceDocumentsChain) {
if (!data.llm_chain) {
throw new Error("Missing llm_chain");
}
if (!data.combine_document_chain) {
throw new Error("Missing combine_document_chain");
}
return new MapReduceDocumentsChain({
llmChain: await LLMChain.deserialize(data.llm_chain),
combineDocumentChain: await StuffDocumentsChain.deserialize(
data.combine_document_chain
),
});
}
serialize(): SerializedMapReduceDocumentsChain {
return {
_type: this._chainType(),
llm_chain: this.llmChain.serialize(),
combine_document_chain: this.combineDocumentChain.serialize(),
};
}
}
/**
* Interface for the input properties of the RefineDocumentsChain class.
*/
export interface RefineDocumentsChainInput extends StuffDocumentsChainInput {
refineLLMChain: LLMChain;
documentPrompt?: BasePromptTemplate;
initialResponseName?: string;
documentVariableName?: string;
outputKey?: string;
}
/**
* Combine documents by doing a first pass and then refining on more documents.
* @augments BaseChain
* @augments RefineDocumentsChainInput
*/
export class RefineDocumentsChain
extends BaseChain
implements RefineDocumentsChainInput
{
static lc_name() {
return "RefineDocumentsChain";
}
llmChain: LLMChain;
inputKey = "input_documents";
outputKey = "output_text";
documentVariableName = "context";
initialResponseName = "existing_answer";
refineLLMChain: LLMChain;
get defaultDocumentPrompt(): BasePromptTemplate {
return new PromptTemplate({
inputVariables: ["page_content"],
template: "{page_content}",
});
}
documentPrompt = this.defaultDocumentPrompt;
get inputKeys() {
return [
...new Set([
this.inputKey,
...this.llmChain.inputKeys,
...this.refineLLMChain.inputKeys,
]),
].filter(
(key) =>
key !== this.documentVariableName && key !== this.initialResponseName
);
}
get outputKeys() {
return [this.outputKey];
}
constructor(fields: RefineDocumentsChainInput) {
super(fields);
this.llmChain = fields.llmChain;
this.refineLLMChain = fields.refineLLMChain;
this.documentVariableName =
fields.documentVariableName ?? this.documentVariableName;
this.inputKey = fields.inputKey ?? this.inputKey;
this.outputKey = fields.outputKey ?? this.outputKey;
this.documentPrompt = fields.documentPrompt ?? this.documentPrompt;
this.initialResponseName =
fields.initialResponseName ?? this.initialResponseName;
}
/** @ignore */
async _constructInitialInputs(doc: Document, rest: Record<string, unknown>) {
const baseInfo: Record<string, unknown> = {
page_content: doc.pageContent,
...doc.metadata,
};
const documentInfo: Record<string, unknown> = {};
this.documentPrompt.inputVariables.forEach((value) => {
documentInfo[value] = baseInfo[value];
});
const baseInputs: Record<string, unknown> = {
[this.documentVariableName]: await this.documentPrompt.format({
...documentInfo,
}),
};
const inputs = { ...baseInputs, ...rest };
return inputs;
}
/** @ignore */
async _constructRefineInputs(doc: Document, res: string) {
const baseInfo: Record<string, unknown> = {
page_content: doc.pageContent,
...doc.metadata,
};
const documentInfo: Record<string, unknown> = {};
this.documentPrompt.inputVariables.forEach((value) => {
documentInfo[value] = baseInfo[value];
});
const baseInputs: Record<string, unknown> = {
[this.documentVariableName]: await this.documentPrompt.format({
...documentInfo,
}),
};
const inputs = { [this.initialResponseName]: res, ...baseInputs };
return inputs;
}
/** @ignore */
async _call(
values: ChainValues,
runManager?: CallbackManagerForChainRun
): Promise<ChainValues> {
if (!(this.inputKey in values)) {
throw new Error(`Document key ${this.inputKey} not found.`);
}
const { [this.inputKey]: docs, ...rest } = values;
const currentDocs = docs as Document[];
const initialInputs = await this._constructInitialInputs(
currentDocs[0],
rest
);
let res = await this.llmChain.predict(
{ ...initialInputs },
runManager?.getChild("answer")
);
const refineSteps = [res];
for (let i = 1; i < currentDocs.length; i += 1) {
const refineInputs = await this._constructRefineInputs(
currentDocs[i],
res
);
const inputs = { ...refineInputs, ...rest };
res = await this.refineLLMChain.predict(
{ ...inputs },
runManager?.getChild("refine")
);
refineSteps.push(res);
}
return { [this.outputKey]: res };
}
_chainType() {
return "refine_documents_chain" as const;
}
static async deserialize(data: SerializedRefineDocumentsChain) {
const SerializedLLMChain = data.llm_chain;
if (!SerializedLLMChain) {
throw new Error("Missing llm_chain");
}
const SerializedRefineDocumentChain = data.refine_llm_chain;
if (!SerializedRefineDocumentChain) {
throw new Error("Missing refine_llm_chain");
}
return new RefineDocumentsChain({
llmChain: await LLMChain.deserialize(SerializedLLMChain),
refineLLMChain: await LLMChain.deserialize(SerializedRefineDocumentChain),
});
}
serialize(): SerializedRefineDocumentsChain {
return {
_type: this._chainType(),
llm_chain: this.llmChain.serialize(),
refine_llm_chain: this.refineLLMChain.serialize(),
};
}
}