Avoid re-introspecting on every query

src/index.js

@@ -3,6 +3,7 @@
 const assert = require("assert");
 const matchValue = require("match-value");
 const dbErrors = require("db-errors");
+const DataLoader = require("dataloader");
 
 const knexIntrospect = require("./introspect");
 const dataloaderFromKnexResults = require("./dataloader-from-knex-results");
@@ -94,8 +95,13 @@ module.exports = {
 		};
 	},
 	generateModule: async function generate(globalKnex, tableName, relations = {}) {
+		// Make sure we only look up each table once, even when resolving relations
+		let introspectLoader = new DataLoader((tables) => {
+			return Promise.all(tables.map((table) => knexIntrospect(globalKnex, table)));
+		});
+
 		// relations: { columnName: [ belongsTo, hasMany ] }, eg. on a posts table, it might have { thread_id: [ "thread", "posts" ] }
-		let tableLayout = await knexIntrospect(globalKnex, tableName);
+		let tableLayout = await introspectLoader.load(tableName);
 	
 		let fieldNames = Object.keys(tableLayout);
 		let primaryKeyColumn = Object.values(tableLayout).find((props) => props.isPrimaryKey === true);
@@ -161,7 +167,7 @@ module.exports = {
 						for (let name of Object.keys(relations)) {
 							let localField = relations[name][0]; // eg. "thread"
 							let foreignKey = tableLayout[name].foreignKey;
-							let remoteTableLayout = await knexIntrospect(globalKnex, foreignKey.table);
+							let remoteTableLayout = await introspectLoader.load(foreignKey.table);
 	
 							if (remoteTableLayout[foreignKey.column].isPrimaryKey === true) {
 								let field = [ localField, async function (_, { $make, $getProperty }) {