message: [schemadb] use GetIntProperty to get live data size of some cf
  simpler way to do this.
diff: @@ -17,7 +17,7 @@ pub mod schema;
  use crate::schema::{KeyCodec, Schema, SeekKeyCodec, ValueCodec};
  use failure::prelude::*;
  use rocksdb::{
  - rocksdb_options::ColumnFamilyDescriptor, CFHandle, DBOptions, Range, Writable, WriteOptions,
  + rocksdb_options::ColumnFamilyDescriptor, CFHandle, DBOptions, Writable, WriteOptions,
  };
  use std::{
  collections::{BTreeMap, HashMap},
  @@ -283,21 +283,9 @@ impl DB {
  for cf_name in self.inner.cf_names().into_iter().map(ToString::to_string) {
  let cf_handle = self.get_cf_handle(&cf_name)?;
  - let first_key = match self.get_first_key(cf_handle) {
  - Some(key) => key,
  - None => {
  - cf_sizes.insert(cf_name, 0);
  - continue;
  - }
  - };
  - let last_key = self
  - .get_last_key(cf_handle)
  - .ok_or_else(|| format_err!("Found first key but not last key."))?;
  - let range = Range::new(&first_key, &last_key);
  let size = self
  .inner
  - .get_approximate_sizes_cf(cf_handle, &[range])
  - .pop()
  + .get_property_int_cf(cf_handle, "rocksdb.estimate-live-data-size")
  .ok_or_else(|| {
  format_err!(
  "Unable to get approximate size of {} column family.",
  @@ -310,20 +298,6 @@ impl DB {
  Ok(cf_sizes)
  }
  - /// Returns the first key in given column family, if it exists.
  - fn get_first_key(&self, cf_handle: &CFHandle) -> Option<Vec<u8>> {
  - let mut iter = self.inner.iter_cf(cf_handle);
  - iter.seek(rocksdb::SeekKey::Start);
  - iter.kv().map(|(key, _value)| key)
  - }
  -
  - /// Returns the last key in given column family, if it exists.
  - fn get_last_key(&self, cf_handle: &CFHandle) -> Option<Vec<u8>> {
  - let mut iter = self.inner.iter_cf(cf_handle);
  - iter.seek(rocksdb::SeekKey::End);
  - iter.kv().map(|(key, _value)| key)
  - }
  -
  /// Flushes all memtable data. If `sync` is true, the flush will wait until it's done. This is
  /// only used for testing `get_approximate_sizes_cf` in unit tests.
  pub fn flush_all(&self, sync: bool) -> Result<()> {
  