feat: add scalar functions in postgres (#165)

- Implemented only conditional and stringEquals function based on projection function support required for QS(as per attribute service)

query-service-impl/src/main/java/org/hypertrace/core/query/service/postgres/converters/PostgresFunctionConverter.java

@@ -3,7 +3,6 @@
 import static org.hypertrace.core.query.service.QueryFunctionConstants.DATE_TIME_CONVERT;
 import static org.hypertrace.core.query.service.QueryFunctionConstants.QUERY_FUNCTION_AVGRATE;
 import static org.hypertrace.core.query.service.QueryFunctionConstants.QUERY_FUNCTION_CONCAT;
-import static org.hypertrace.core.query.service.QueryFunctionConstants.QUERY_FUNCTION_CONDITIONAL;
 import static org.hypertrace.core.query.service.QueryFunctionConstants.QUERY_FUNCTION_COUNT;
 import static org.hypertrace.core.query.service.QueryFunctionConstants.QUERY_FUNCTION_DISTINCTCOUNT;
 import static org.hypertrace.core.query.service.QueryFunctionConstants.QUERY_FUNCTION_PERCENTILE;
@@ -60,8 +59,6 @@ public String convert(
         return this.functionToStringForAvgRate(function, argumentConverter, executionContext);
       case DATE_TIME_CONVERT:
         return this.functionToDateTimeConvert(function, argumentConverter);
-      case QUERY_FUNCTION_CONDITIONAL:
-        throw new UnsupportedOperationException("Unsupported function " + function);
       default:
         // TODO remove once postgres-specific logic removed from gateway - this normalization
         // reverts that logic

query-service-impl/src/test/java/org/hypertrace/core/query/service/postgres/QueryRequestToPostgresSQLConverterTest.java

@@ -975,8 +975,17 @@ void testQueryWithNulls() {
     TableDefinition tableDefinition = getDefaultTableDefinition();
     defaultMockingForExecutionContext();
 
-    assertExceptionOnSQLQuery(
-        queryRequest, UnsupportedOperationException.class, "Unsupported function");
+    assertSQLQuery(
+        queryRequest,
+        "select conditional('true',encode(span_id, 'hex'),'null'), conditional('true',duration_millis,0)"
+            + " from public.\"span-event-view\""
+            + " where "
+            + tableDefinition.getTenantIdColumn()
+            + " = '"
+            + TENANT_ID
+            + "' limit 15",
+        tableDefinition,
+        executionContext);
   }
 
   @Test

query-service/src/integrationTest/resources/sql/functions.sql

@@ -1 +1,31 @@
-CREATE OR REPLACE FUNCTION dateTimeConvert (bigint, bigint) RETURNS bigint AS $$ select ((($1 + $2 - 1)/$2)*$2) $$ LANGUAGE SQL;
+CREATE OR REPLACE FUNCTION dateTimeConvert (bigint, bigint) RETURNS bigint AS $$ select ((($1 + $2 - 1)/$2)*$2) $$ LANGUAGE SQL;
+
+CREATE OR REPLACE FUNCTION conditional (condition text, first text, second text)
+ RETURNS text
+  AS $$
+   SELECT
+    CASE WHEN condition IS NOT NULL
+     THEN CASE WHEN CAST (condition AS BOOLEAN) THEN first ELSE second END
+     ELSE NULL
+    END
+  $$
+  LANGUAGE SQL;
+
+CREATE OR REPLACE FUNCTION stringEquals (str1 text, str2 text)
+ RETURNS text
+  AS $$
+   SELECT
+    CASE WHEN str1 IS NULL AND str2 IS NULL
+     THEN 'true'
+     ELSE
+      CASE WHEN str1 IS NULL OR str2 IS NULL
+       THEN 'false'
+       ELSE
+        CASE WHEN str1 = str2
+         THEN 'true'
+         ELSE 'false'
+        END
+      END
+    END
+  $$
+  LANGUAGE SQL;