uast2clickhouse

The CLI tool to put Babelfish's UASTs to ClickHouse DB.

It is written in Go and has zero dependencies. The list of solved problems includes:

• Normalizing the UAST even stronger than in the Semantic mode.
• Converting a tree structure to a linear list of "interesting" nodes.
• Handling runtime errors which are typical to big data processing: OOMs, crashes, DB insertion failures, etc.
• Running distributed and unattended.

Installation

You need a Go compiler >=1.11.

export GO111MODULE=on
go build uast2clickhouse

Usage

Install ClickHouse >= 19.4 and initialize the DB schema:

clickhouse-client --query="CREATE TABLE uasts (
  id Int32,
  left Int32,
  right Int32,
  repo String,
  lang String,
  file String,
  line Int32,
  parents Array(Int32),
  pkey String,
  roles Array(Int16),
  type String,
  orig_type String,
  uptypes Array(String),
  value String
) ENGINE = MergeTree() ORDER BY (repo, file, id);

CREATE TABLE meta (
   repo String,
   siva_filenames Array(String),
   file_count Int32,
   langs Array(String),
   langs_bytes_count Array(UInt32),
   langs_lines_count Array(UInt32),
   langs_files_count Array(UInt32),
   commits_count Int32,
   branches_count Int32,
   forks_count Int32,
   empty_lines_count Array(UInt32),
   code_lines_count Array(UInt32),
   comment_lines_count Array(UInt32),
   license_names Array(String),
   license_confidences Array(Float32),
   stars Int32,
   size Int64,
   INDEX stars stars TYPE minmax GRANULARITY 1
) ENGINE = MergeTree() ORDER BY repo;"

Then run on each of the nodes

./uast2clickhouse --heads heads.csv --db default:password@10.150.0.9/default /path/to/parquet

or

./uast2clickhouse --heads heads.csv --db default:password@10.150.0.9/default 10.150.0.9:11300

heads.csv contain the mapping from the HEAD UUIDs in Parquet to the actual repository names. If you work with PGA, download it or generate with list-pga-heads. --db default:password@10.150.0.9/default is the ClickHouse connection string. 10.150.0.9:11300 is a sample beanstalkd message queue address for distributed processing. You should specify --read-streams and --db-streams to reach the peak performance. --read-streams sets the number of goroutines to read the Parquet file, and --db-streams set the number of HTTP threads which upload the SQL insertions to ClickHouse. Usually --db-streams is bigger than --read-streams. The bigger values increase the memory pressure.

Sample operation

Input: UASTs extracted from PGA'19, 204068 Parquet files overall in a 6 TB Google Cloud volume. DB instance configuration: Google Cloud "highcpu" with 64 cores, 58GB of RAM. 6 local NVMe SSDs joined in RAID0 and formatted to ext4 with journal disabled. Ubuntu 18.04. Worker configuration: Ubuntu 18.04 with 20GB of SSD disk and the UASTs volume attached read-only at /mnt/uasts.

• Install and run beanstalkd on the DB instance. Build locally and scp there the beanstool binary.
• List all the Parquet files with find /mnt/uasts -name '*.parquet' | gzip > tasks.gz on one of the workers.
• scp tasks.gz to the DB instance. zcat tasks.gz | xargs -n1 ./beanstool put --ttr 1000h -t default -b to fill the queue.
• Install and setup ClickHouse on the DB instance. There are sample /etc/clickhouse-server/config.xml and /etc/clickhouse-server/users.xml.
• Execute the pushing procedure in 4 stages.

1. 16 workers, 2 cores, 4 GB RAM each. ./uast2clickhouse --read-streams 2 --db-streams 6 --heads heads.csv --db default:password@10.150.0.9/default 10.150.0.9:11300. This succeeds with ~80% of the tasks. Then ./beanstool kick --num NNN -t default.
2. 16 workers, 2 cores, 4 GB RAM each. ./uast2clickhouse --read-streams 1 --db-streams 1 --heads heads.csv --db default:password@10.150.0.9/default 10.150.0.9:11300. This succeeds with all but 1k tasks.
3. 16 workers, 2 cores, 16 GB RAM each ("highmem"). Same command. This leaves only ~10 tasks.
4. 2 workers, 4 cores, 32 GB RAM each ("highmem"). Same command, full success.

• Create the secondary DB indexes.

SET allow_experimental_data_skipping_indices = 1;
ALTER TABLE uasts ADD INDEX lang lang TYPE set(0) GRANULARITY 1;
ALTER TABLE uasts ADD INDEX type type TYPE set(0) GRANULARITY 1;
ALTER TABLE uasts ADD INDEX value_exact value TYPE bloom_filter() GRANULARITY 1;
ALTER TABLE uasts ADD INDEX left (repo, file, left) TYPE minmax GRANULARITY 1;
ALTER TABLE uasts ADD INDEX right (repo, file, right) TYPE minmax GRANULARITY 1;
ALTER TABLE uasts MATERIALIZE INDEX lang;
ALTER TABLE uasts MATERIALIZE INDEX type;
ALTER TABLE uasts MATERIALIZE INDEX value_exact;
ALTER TABLE uasts MATERIALIZE INDEX left;
ALTER TABLE uasts MATERIALIZE INDEX right;
OPTIMIZE TABLE uasts FINAL;

The whole thing takes ~1 week.

Tests

There are sadly no tests at the moment. We are going to fix this.

License

Apache 2.0, see LICENSE.