HeartSaVioR commented on a change in pull request #24173: [SPARK-27237][SS]
Introduce State schema validation among query restart
URL: https://github.com/apache/spark/pull/24173#discussion_r269054217
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/StateSchemaCompatibilityChecker.scala
##########
@@ -40,14 +40,19 @@ class StateSchemaCompatibilityChecker(
logDebug(s"Schema file for provider $providerId exists. Comparing with
provided schema.")
val (storedKeySchema, storedValueSchema) = readSchemaFile()
- def fieldToType: StructField => (DataType, Boolean) = f => (f.dataType,
f.nullable)
-
- def typesEq(schema1: StructType, schema2: StructType): Boolean = {
- (schema1.length == schema2.length) && schema1.map(fieldToType) ==
schema2.map(fieldToType)
+ def fieldCompatible(fieldOld: StructField, fieldNew: StructField):
Boolean = {
+ // compatibility for nullable
+ // - same: OK
+ // - non-nullable -> nullable: OK
+ // - nullable -> non-nullable: Not compatible
+ (fieldOld.dataType == fieldNew.dataType) &&
+ ((fieldOld.nullable == fieldNew.nullable) ||
+ (!fieldOld.nullable && fieldNew.nullable))
}
- def namesEq(schema1: StructType, schema2: StructType): Boolean = {
- schema1.fieldNames.sameElements(schema2.fieldNames)
+ def schemaCompatible(schemaOld: StructType, schemaNew: StructType):
Boolean = {
+ (schemaOld.length == schemaNew.length) &&
Review comment:
Undefined behavior, as state would be stored in file as unsafe byte array,
and we just rely on new schema to parse it. It might be fine while reading if
all column(s) is(are) dropped from rightmost, but the some of information in
row (like numFields) would be incorrect so not sure which operation refers it
and finally make query crash. If column(s) is(are) dropped from other spots,
query would be crashed sooner.
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