add string agg function (dataform-co#1094)

* add string agg function

* fix spelling mistake in README

* another sp

* omit redshift for test

* switch != to !==

Co-authored-by: Dan Lee <[email protected]>

packages/@dataform/sql/BUILD

@@ -22,7 +22,7 @@ pkg_json(
     ],
     main = "bundle.js",
     types = "bundle.d.ts",
-    version = "0.2.0",
+    version = "0.3.0",
 )
 
 pkg_bundle(

sql/README → sql/README.md

@@ -6,7 +6,7 @@ Useful functions for constructing SQL statements in Dataform packages.
 - Redshift
 - Snowflake
 
-*If you would like us to add support for another warehouse, please get in touch via [email](mailto:[email protected]) or [Slack](https://dataform.co/slack)*
+_If you would like us to add support for another warehouse, please get in touch via [email](mailto:[email protected]) or [Slack](https://dataform.co/slack)_
 
 ## Installation
 
@@ -17,34 +17,35 @@ Useful functions for constructing SQL statements in Dataform packages.
 ### Common SQL functions
 
 #### surrogateKey
+
 Creates a unique hash from a list of fields. Useful for generating a surrogate key for a table.
 
 `${sql.surrogateKey(["field_one", "field_two"])}`
 
 #### windowFunction
+
 Creates a window function with the given configuration.
 
-`${sql.windowFunction({
-  name: "window_function_name",
-  value: "target_column",
-  ignoreNulls: true,
-  windowSpecification: {
-    partitionFields: ["field_to_partition_by_one", "field_to_partition_by_two"],
-    orderFields: ["field_to_order_by_one", "field_to_order_by_two"],
-    frameClause: "rows between 0 preceding and unbounded following"
-  }
-})}`
+`${sql.windowFunction({ name: "window_function_name", value: "target_column", ignoreNulls: true, windowSpecification: { partitionFields: ["field_to_partition_by_one", "field_to_partition_by_two"], orderFields: ["field_to_order_by_one", "field_to_order_by_two"], frameClause: "rows between 0 preceding and unbounded following" } })}`
 
 #### asTimestamp
+
 Casts the field to timestamp type
 
 `${sql.asTimestamp("field")}`
 
 #### asString
+
 Casts the field to timestamp type
 
 `${sql.asString("field")}`
 
+#### stringAgg
+
+Groups the values in a field into a concatenated string, with an optional delimiter value that defaults to ","
+
+`${sql.stringAgg("field", "delimiter")}`
+
 ### Timestamp functions
 
 Calculate the time difference between two timestamps.

sql/index.ts

@@ -227,6 +227,15 @@ export class Sql {
     }
   }
 
+  // String aggregation
+
+  public stringAgg(field: string, delimiter = ",") {
+    if (this.dialect === "snowflake" || this.dialect === "redshift") {
+      return `listagg(${field}, '${delimiter}')`;
+    }
+    return `string_agg(${field}, '${delimiter}')`;
+  }
+
   // Convenience methods for builders.
   public json<S extends ISelectSchema>(data: S[]) {
     return new JSONBuilder<S>(this, data);

sql/integration.spec.ts

@@ -240,6 +240,31 @@ suite("builders", { parallel: true }, ({ before, after }) => {
         expect(result[0].max).equals(1);
         expect(result[0].first_value).equals(1);
       });
+      // skipping this test for redshift as the function is only supported on user-defined-tables
+      // i.e. not when just querying a select statement with no table
+      if (name !== "redshift") {
+        test("string agg", async () => {
+          const rows = [
+            {
+              a: "foo"
+            },
+            {
+              a: "bar"
+            }
+          ];
+          const query = sql.from(sql.json(rows)).select({
+            agg: sql.stringAgg("a"),
+            agg_hyphen: sql.stringAgg("a", "-")
+          });
+
+          const result: any = await execute(query);
+          expect(result.length).equals(1);
+          expect(result[0]).deep.equals({
+            agg: "foo,bar",
+            agg_hyphen: "foo-bar"
+          });
+        });
+      }
 
       test("timestamp diff", async () => {
         const rows = [