feat: support merge small write requests (apache#879)

analytic_engine/src/instance/mod.rs

@@ -143,6 +143,7 @@ pub struct Instance {
     meta_cache: Option<MetaCacheRef>,
     /// Engine memtable memory usage collector
     mem_usage_collector: Arc<MemUsageCollector>,
+    pub(crate) max_rows_in_write_queue: usize,
     /// Engine write buffer size
     pub(crate) db_write_buffer_size: usize,
     /// Space write buffer size

analytic_engine/src/instance/open.rs

@@ -120,6 +120,7 @@ impl Instance {
             file_purger,
             meta_cache: ctx.meta_cache.clone(),
             mem_usage_collector: Arc::new(MemUsageCollector::default()),
+            max_rows_in_write_queue: ctx.config.max_rows_in_write_queue,
             db_write_buffer_size: ctx.config.db_write_buffer_size,
             space_write_buffer_size: ctx.config.space_write_buffer_size,
             replay_batch_size: ctx.config.replay_batch_size,

analytic_engine/src/lib.rs

@@ -61,6 +61,8 @@ pub struct Config {
     /// Manifest options
     pub manifest: ManifestOptions,
 
+    /// The maximum rows in the write queue.
+    pub max_rows_in_write_queue: usize,
     /// The maximum write buffer size used for single space.
     pub space_write_buffer_size: usize,
     /// The maximum size of all Write Buffers across all spaces.
@@ -108,6 +110,7 @@ impl Default for Config {
             sst_meta_cache_cap: Some(1000),
             sst_data_cache_cap: Some(1000),
             manifest: ManifestOptions::default(),
+            max_rows_in_write_queue: 0,
             /// Zero means disabling this param, give a positive value to enable
             /// it.
             space_write_buffer_size: 0,