feat: RDS variableMap support (#121)

* adds support for variableMap in VTL templates

* Adds simple documentation on variableMap usage for RDS DL

* Cleanup

* just to avoid confusion

* cleanup

* cleanup

* Adds back console on error

* linting...

* Feedback from code review

* oops

* Comments from Jariz

* Replace all boolean and null variables

Author: katesclau

README.md

@@ -366,6 +366,25 @@ This plugin supports resolvers implemented by `amplify-appsync-simulator`, as we
 $utils.toJson($response)
 ```
 
+### Using Variable Map
+Variable map support is limited and does not differentiate numbers and strings data types, please inject them directly if needed.
+
+Will be escaped properly: `null`, `true`, and `false` values.
+
+```
+{
+  "version": "2018-05-29",
+  "statements":   [
+    "UPDATE <name-of-table> set deleted_at=NOW() WHERE id=:ID", 
+    "SELECT * FROM <name-of-table> WHERE id=:ID and unix_timestamp > $ctx.args.newerThan"
+  ],
+  variableMap: {
+    ":ID": $ctx.args.id,
+##    ":TIMESTAMP": $ctx.args.newerThan -- This will be handled as a string!!!
+  }
+}
+```
+
 ## Contributors ✨
 
 Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):

src/data-loaders/RelationalDataLoader.js

@@ -74,9 +74,10 @@ const convertSQLResponseToRDSRecords = (rows) => {
 
 const convertPostgresSQLResponseToColumnMetaData = (rows) => {
   return rows.map((row) => {
-    const typeName = Object.keys(pgTypes.builtins)
-      .find((d) => pgTypes.builtins[d] === row.dataTypeID)
-      .toUpperCase();
+    const typeName =
+      Object.keys(pgTypes.builtins).find(
+        (d) => pgTypes.builtins[d] === row.dataTypeID,
+      ) ?? 'UNKNOWN';
     // @TODO: Add support for the following fields
     // isAutoIncrement,
     // nullable,
@@ -98,8 +99,34 @@ const convertPostgresSQLResponseToColumnMetaData = (rows) => {
     };
   });
 };
+
+const injectVariables = (statement, req) => {
+  const { variableMap } = req;
+  if (!variableMap) {
+    return statement;
+  }
+  const result = Object.keys(variableMap).reduce((statmnt, key) => {
+    if (variableMap[key] === null || typeof variableMap[key] == 'boolean') {
+      return statmnt.replaceAll(key, `${variableMap[key]}`);
+    }
+    // @TODO: Differentiate number from string inputs...
+    return statmnt.replaceAll(key, `'${variableMap[key]}'`);
+  }, statement);
+  return result;
+};
+
 const executeSqlStatements = async (client, req) =>
-  Promise.mapSeries(req.statements, (statement) => client.query(statement));
+  Promise.mapSeries(req.statements, async (statement) => {
+    statement = injectVariables(statement, req);
+    try {
+      const result = await client.query(statement);
+      return result;
+    } catch (error) {
+      console.log(`RDS_DATALOADER: Failed to execute: `, statement, error);
+      throw error;
+    }
+  });
+
 export default class RelationalDataLoader {
   constructor(config) {
     this.config = config;
@@ -132,7 +159,6 @@ export default class RelationalDataLoader {
         database: this.config.rds.dbName,
         port: this.config.rds.dbPort,
       };
-
       const res = {};
       if (this.config.rds.dbDialect === 'mysql') {
         const client = await mysql.createConnection(dbConfig);