tests: add a test case showing restoring 300 small tables is fast

tests/br_300_small_tables/run.sh

@@ -0,0 +1,47 @@
+#!/bin/sh
+#
+# Copyright 2020 PingCAP, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -eu
+DB="$TEST_NAME"
+TABLES_COUNT=300
+
+run_sql "create schema $DB;"
+
+# generate 300 tables with 1 row content.
+i=1
+while [ $i -le $TABLES_COUNT ]; do
+    run_sql "create table $DB.sbtest$i(id int primary key, k int not null, c char(120) not null, pad char(60) not null);"
+    run_sql "insert into $DB.sbtest$i values ($i, $i, '$i', '$i');"
+    i=$(($i+1))
+done
+
+# backup db
+echo "backup start..."
+run_br backup db --db "$DB" -s "local://$TEST_DIR/$DB" --pd $PD_ADDR
+
+# truncate every table
+# (FIXME: drop instead of truncate. if we drop then create-table will still be executed and wastes time executing DDLs)
+i=1
+while [ $i -le $TABLES_COUNT ]; do
+    run_sql "truncate $DB.sbtest$i;"
+    i=$(($i+1))
+done
+
+# restore db
+# (FIXME: shouldn't need --no-schema to be fast, currently the alter-auto-id DDL slows things down)
+echo "restore start..."
+run_br restore db --db $DB -s "local://$TEST_DIR/$DB" --pd $PD_ADDR --no-schema
+
+run_sql "DROP DATABASE $DB;"