fix: allow empty structs in schema inference (#5656)

confluentinc · Jun 19, 2020 · 3c38c8c · 3c38c8c
1 parent b5cc092
commit 3c38c8c
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Showing 4 changed files with 19 additions and 1 deletion.
diff --git a/ksqldb-common/src/main/java/io/confluent/ksql/schema/connect/SqlSchemaFormatter.java b/ksqldb-common/src/main/java/io/confluent/ksql/schema/connect/SqlSchemaFormatter.java
@@ -161,6 +161,9 @@ public String visitMap(final Schema schema, final String key, final String value
     }
 
     public String visitStruct(final Schema schema, final List<? extends String> fields) {
+      if (fields.isEmpty()) {
+        return "STRUCT< >";
+      }
       return fields.stream()
           .collect(Collectors.joining(", ", STRUCT_START, STRUCTURED_END));
     }

diff --git a/ksqldb-common/src/test/java/io/confluent/ksql/schema/connect/SqlSchemaFormatterTest.java b/ksqldb-common/src/test/java/io/confluent/ksql/schema/connect/SqlSchemaFormatterTest.java
@@ -172,6 +172,15 @@ public void shouldFormatOptionalMap() {
     assertThat(STRICT.format(schema), is("MAP<VARCHAR, DOUBLE>"));
   }
 
+  @Test
+  public void shouldFormatEmptyStruct() {
+    // Given:
+    final Schema struct = SchemaBuilder.struct().optional().build();
+
+    // Then:
+    assertThat(DEFAULT.format(struct), is("STRUCT< >"));
+  }
+
   @Test
   public void shouldFormatStruct() {
     // Given:

diff --git a/...est/java/io/confluent/ksql/schema/ksql/inference/DefaultSchemaInjectorFunctionalTest.java b/...est/java/io/confluent/ksql/schema/ksql/inference/DefaultSchemaInjectorFunctionalTest.java
@@ -396,6 +396,12 @@ public void shouldIgnoreConnectMapWithUnsupportedKey() {
     );
   }
 
+  @Test
+  public void shouldInferEmptyStruct() {
+    final Schema emptyStruct = SchemaBuilder.struct().optional().build();
+    shouldInferConnectType(emptyStruct, emptyStruct);
+  }
+
   @Test
   public void shouldInferComplexConnectSchema() {
     final Schema arrayInner = SchemaBuilder.struct()

diff --git a/...rces/historical_plans/create-struct_-_empty_struct_creation/5.5.0_1581572087372/spec.json b/...rces/historical_plans/create-struct_-_empty_struct_creation/5.5.0_1581572087372/spec.json
@@ -101,7 +101,7 @@
   } ],
   "schemas" : {
     "CSAS_BIG_STRUCT_0.KsqlTopic.Source" : "STRUCT<COL1 VARCHAR> NOT NULL",
-    "CSAS_BIG_STRUCT_0.BIG_STRUCT" : "STRUCT<S STRUCT<>> NOT NULL"
+    "CSAS_BIG_STRUCT_0.BIG_STRUCT" : "STRUCT<S STRUCT< >> NOT NULL"
   },
   "configs" : {
     "ksql.extension.dir" : "ext",