如何从作为库运行的postgraphile中获取查询结果

Question

我已经将postgraphile作为快速中间件运行。例如：

const pgMiddleware = postgraphile(pool, SCHEMA, postgraphileConfig);

app.use(pgMiddleware);

如何在没有单独的客户端的情况下获取或拦截查询或突变的结果数据？

例如，当我发送以下查询时

query {
 personById(id: 1){
  firstname
  }
}

I want to be able to get the data sent back inside the same express app.

Answer 1

我相信您所要求的是能够对来自Express中其他路由/中间件的PostGraphile模式执行PostGraphile操作，而不需要提出额外的http请求。这称为模式仅使用，您将特别希望使用withPostGraphileContext来执行请求和处理结果：

import type { Express } from "express";
import type { Pool } from "pg";
import {
  gql,
  makeProcessSchemaPlugin,
  postgraphile,
  withPostGraphileContext,
} from "postgraphile";
import PgSimplifyInflectorPlugin from "@graphile-contrib/pg-simplify-inflector";
import type { GraphQLSchema } from "graphql";
import { graphql } from "graphql";

// Register your middlewares with express
const schemaOnlyUsageApp = (app: Express, pool: Pool) => {
  let schema: GraphQLSchema;

  // This plugin will execute a callback each time the PostGraphile
  // GraphQl schema is rebuit.
  const schemaProcessorPlugin = makeProcessSchemaPlugin((newSchema) => {
    schema = newSchema;
    return schema;
  });

  // Register the PostGraphile middleware as normal for requests on /graphql (and /graphiql)
  app.use(
    postgraphile(pool, "my_schema", {
      simpleCollections: "omit",
      dynamicJson: true,
      legacyRelations: "omit",
      setofFunctionsContainNulls: false,
      appendPlugins: [PgSimplifyInflectorPlugin, schemaProcessorPlugin],
      watchPg: true,
      graphiql: true,
      enhanceGraphiql: true,
      showErrorStack: true,
      allowExplain: true,
    })
  );

  // custom route that will execute a predefined gql query directly against the schema
  app.get("/posts", async (req, res) => {
    // arbitrary gql query
    const query = gql`
      query posts {
        posts {
          edges {
            node {
              id
              title
              body
              likeCount
              createdAt
            }
          }
        }
      }
    `;

    const result = await withPostGraphileContext(
      {
        // Reuse your pool to avoid creating additional connections
        pgPool: pool,
      },
      async (context) => {
        // execute your query directly and get results without making
        // an additional http request!
        const queryResult = await graphql({
          schema,
          source: query.loc?.source || "",
          contextValue: { ...context },
        });
        return queryResult;
      }
    );

    res.send(result);
  });
};

export default schemaOnlyUsageApp;