import: fix #4257, restrict memory usage by RocksDB (#4350)

* import: put index and filter in block cache to restrict memory usage

Signed-off-by: Lonng <chris@lonng.org>

src/import/engine.rs

@@ -292,9 +292,10 @@ fn tune_dboptions_for_bulk_load(opts: &DbConfig) -> (DBOptions, CFOptions) {
     // RocksDB preserves `max_background_jobs/4` for flush.
     db_opts.set_max_background_jobs(opts.max_background_jobs);
 
+    // Put index and filter in block cache to restrict memory usage.
     let mut block_base_opts = BlockBasedOptions::new();
-    // Use a large block size for sequential access.
-    block_base_opts.set_block_size(MB as usize);
+    block_base_opts.set_lru_cache(128 * MB as usize, -1, 0, 0.0);
+    block_base_opts.set_cache_index_and_filter_blocks(true);
     let mut cf_opts = ColumnFamilyOptions::new();
     cf_opts.set_block_based_table_factory(&block_base_opts);
     cf_opts.compression_per_level(&opts.defaultcf.compression_per_level);