[#14163] yql - Improve logging in case of duplicate index error

Summary: We show the client the same error message indicating a unique constraint error any time a unique index operation failed and the response explicitly set applied=false. While these conditions would only be met in the case of a duplicate value error, the code here invited speculation that we might be masking the true error which may be different. This revision provides an improved explanation of why this branch is ok to assume this is a unique index constraint error and adds additional VLOGs in case the doubt ever rises in production.

Test Plan: Jenkins

Reviewers: pjain, amitanand

Reviewed By: amitanand

Subscribers: kannan

Differential Revision: https://phabricator.dev.yugabyte.com/D20063

src/yb/docdb/cql_operation.cc

@@ -1458,7 +1458,7 @@ Result<QLWriteRequestPB*> CreateAndSetupIndexInsertRequest(
     RETURN_NOT_OK(expr_executor->EvalCondition(
       index->where_predicate_spec()->where_expr().condition(), new_row,
       &new_row_satisfies_idx_pred));
-    VLOG(1) << "Eval condition on partial index " << new_row_satisfies_idx_pred;
+    VLOG(2) << "Eval condition on partial index " << new_row_satisfies_idx_pred;
     if (index_pred_new_row) {
       *index_pred_new_row = new_row_satisfies_idx_pred;
     }

src/yb/tablet/write_query.cc

@@ -87,7 +87,7 @@ bool CheckSchemaVersion(
     return true;
   }
 
-  DVLOG(1) << " On " << table_info->table_name
+  VLOG(1) << " On " << table_info->table_name
            << " Setting status for write as YQL_STATUS_SCHEMA_VERSION_MISMATCH tserver's: "
            << table_info->schema_version << " vs req's : " << schema_version
            << " is req compatible with prev version: "
@@ -310,7 +310,7 @@ Result<bool> WriteQuery::CqlPrepareExecute() {
   RETURN_NOT_OK(InitExecute(ExecuteMode::kCql));
 
   auto& metadata = *tablet().metadata();
-  DVLOG(2) << "Schema version for  " << metadata.table_name() << ": " << metadata.schema_version();
+  VLOG(2) << "Schema version for  " << metadata.table_name() << ": " << metadata.schema_version();
 
   if (!CqlCheckSchemaVersion()) {
     return false;
@@ -694,12 +694,15 @@ void WriteQuery::CompleteQLWriteBatch(const Status& status) {
         ql_write_op->request().type() == QLWriteRequestPB::QL_STMT_INSERT &&
         ql_write_op->response()->has_applied() && !ql_write_op->response()->applied()) {
       // If this is an insert into a unique index and it fails to apply, report duplicate value err.
-      ql_write_op->response()->set_status(QLResponsePB::YQL_STATUS_USAGE_ERROR);
+      // has_applied is only true if we have evaluated the requests if_expr and is only false if
+      // that if_expr ws not satisfied or if the remote index was unique and had a duplicate value
+      // to the one we're trying to insert here.
+      VLOG(1) << "Could not apply operation to remote index " << AsString(ql_write_op->request())
+               << " due to " << AsString(ql_write_op->response());
       ql_write_op->response()->set_error_message(
           Format("Duplicate value disallowed by unique index $0",
           tablet().metadata()->table_name()));
-      DVLOG(1) << "Could not apply the given operation " << AsString(ql_write_op->request())
-               << " due to " << AsString(ql_write_op->response());
+      ql_write_op->response()->set_status(QLResponsePB::YQL_STATUS_USAGE_ERROR);
     } else if (ql_write_op->rowblock() != nullptr) {
       // If the QL write op returns a rowblock, move the op to the transaction state to return the
       // rows data as a sidecar after the transaction completes.
@@ -821,7 +824,8 @@ void WriteQuery::UpdateQLIndexesFlushed(
     auto* index_response = index_op->mutable_response();
 
     if (index_response->status() != QLResponsePB::YQL_STATUS_OK) {
-      DVLOG(1) << "Got status " << index_response->status() << " for " << AsString(index_op);
+      VLOG(1) << "Got response " << index_response->ShortDebugString()
+              << " for " << AsString(index_op);
       response->set_status(index_response->status());
       response->set_error_message(std::move(*index_response->mutable_error_message()));
     }