Fix #471 - Add UDF for extracting document type and version from wildcard tables (#472)

* Fix #471 - Add UDF for extracting document type and version from wildcard tables

udf/extract_document_type.sql

@@ -0,0 +1,13 @@
+/*
+
+Extract the document type from a table name e.g. _TABLE_SUFFIX.
+
+*/
+CREATE TEMP FUNCTION udf_extract_document_type(table_name STRING) AS (REGEXP_EXTRACT(table_name, r"^(.*)_v.*"));
+-- Tests
+SELECT
+  assert_equals("type", udf_extract_document_type("type_v1")),
+  assert_equals(
+    "namespace__namespace_type",
+    udf_extract_document_type("namespace__namespace_type_v20191031")
+  );

udf/extract_document_version.sql

@@ -0,0 +1,13 @@
+/*
+
+Extract the document version from a table name e.g. _TABLE_SUFFIX.
+
+*/
+CREATE TEMP FUNCTION udf_extract_document_version(table_name STRING) AS (REGEXP_EXTRACT(table_name, r".*_v(.*)$"));
+-- Tests
+SELECT
+  assert_equals("1", udf_extract_document_version("type_v1")),
+  assert_equals(
+    "20191031",
+    udf_extract_document_version("namespace__namespace_type_v20191031")
+  );