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Tools for benchmarking TimescaleDB vs PostgreSQL
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README.md

TimescaleDB vs PostgreSQL Benchmark

Introduction

This repository contains a collection of Go programs that can be used to benchmark TimescaleDB against PostgreSQL on insert, query, and deletion (data retention) performance. Additionally, we provide a data set and queries to allow you to measure performance on the same data we have measured.

Getting Started

You will need the Go runtime (1.6+) installed on the machine you wish to benchmark. You can access this repo via go get:

go get github.com/timescale/benchmark-postgres

There are three programs available for installation under the cmd directory, each of which can be installed with go install:

# Change to program directory
cd $GOPATH/src/github.com/timescale/benchmark-postgres/cmd/timescaledb-benchmark-query
go get .
go install

# Repeat for other programs

Our Dataset

In a discussion of how TimescaleDB compares to PostgreSQL, we used two datasets: one with 100M rows of CPU metrics and one with 1B rows. We have made the 100M row dataset available (link will download 7GB archive) and use it throughout this README as an example. In addition to the data in CSV format, the archive also contains a file to create the table schema we used and a selection of queries we tested.

The rows represent CPU metrics for 4000 hosts over the course of 3 days, 2016-01-01 through 2016-01-03. Each row consists of a timestamp, a host identifier, and 10 CPU metrics. All hosts have a row every 10 seconds for the duration of the 3 days, leading to just over 100M rows of data. The CSV is 20 GB and when imported the database is ~30GB.

To unpack the archive:

tar -vxjf benchmark_postgres.tar.bz2

This will unpack the following files into your current directory:

  • cpu-data.csv
  • benchmark-setup-timescaledb.sql
  • benchmark-setup-postgresql.sql
  • queries-1-host-12-hr.sql
  • queries-8-host-1-hr.sql
  • queries-groupby-orderby-limit.sql
  • queries-groupby.sql

Usage

Benchmark: Inserts (timescaledb-parallel-copy)

In the cmd folder is a Git submodule to our parallel copy program that is generally available. This program can actually double as a way to benchmark insert performance in either TimescaleDB or PostgreSQL. Make sure it is installed (see above) and you are ready to go.

Using our 100M dataset, first you need to setup the database and tables. Create a database in PostgreSQL called, e.g., benchmark. Then, setup the tables using our provided schema:

# To setup a TimescaleDB hypertable
psql -d benchmark < benchmark-setup-timescaledb.sql
# To setup a plain PostgreSQL table
psql -d benchmark < benchmark-setup-postgresql.sql

Note that you can setup both tables in the same database for easy comparisons. To measure insert performance, run timescaledb-parallel-copy with the --verbose flag, and optionally a --reporting-period to get in-progress results:

# For TimescaleDB, report every 30s
timescaledb-parallel-copy --db-name=benchmark --table=cpu_ts \
    --verbose --reporting-period=30s --file=cpu-data.csv

# For PostgreSQL, report every 30s
timescaledb-parallel-copy --db-name=benchmark --table=cpu_pg \
    --verbose --reporting-period=30s --file=cpu-data.csv

Once the copy is finished, you'll be given an average number of rows per second over the whole insertion process. If you included a --reporting-period you can also see how the performance changes over time.

at 20s, row rate 137950.621224/sec (period), row rate 137950.621224/sec (overall), 2.760000E+06 total rows
at 40s, row rate 106634.481501/sec (period), row rate 122305.233000/sec (overall), 4.890000E+06 total rows
...
at 14m40s, row rate 97544.843755/sec (period), row rate 112289.740923/sec (overall), 9.877000E+07 total rows
at 15m0s, row rate 134560.614457/sec (period), row rate 112784.651475/sec (overall), 1.014600E+08 total rows
COPY 103680000, took 15m18.895179s with 8 worker(s) (mean rate 112831.150209/sec)

Benchmark: Queries (timescaledb-benchmark-query)

To benchmark query latency, we provide timescaledb-benchmark-query, which takes a file of queries (one per each line) and runs them in parallel. Each query is run twice, to generate 'cold' and 'warm' measurements for each, and the averages of both are printed after all the queries are run:

timescaledb-benchmark-query --db-name=benchmark --table=cpu_ts \
    --query-file=queries-1-host-12-hr.sql --workers=1

avg of 'cold' 10 queries (ms):    19.90
avg of 'warm' 10 queries (ms):    14.50

You can compare these numbers to PostgreSQL by changing the --table flag to point to a plain PostgreSQL table.

Included in our 100M row dataset are queries of 4 types:

  • 1-host-12-hr: Returns the max CPU usage per minute for 12 hours on one host
  • 8-host-1-hr: Same as above except for 8 eights over 1 hour
  • groupby: Returns the avg CPU usage per host per hour over 24 hours
  • groupby-orderby-limit: Returns the last 5 max CPU usage per minute across all devices with a random time range end point

Note: The queries are missing the table name (replaced with %s), which is filled in later by the --table flag to timescaledb-benchmark-query.

Benchmark: Data Retention (timescaledb-benchmark-delete)

Our final benchmark deals with measuring the cost of removing data after it falls outside of a retention period. TimescaleDB introduces a function called drop_chunks() to easily remove data older than a certain date. Combined with the way TimescaleDB organizes and stores data, this is much more efficient for removing data.

To measure this, we provide timescaledb-benchmark-delete which can be used to delete data using drop_chunks() or SQL's DELETE command. Note that this program does actually delete the data, so if you using it, make sure the data loss is okay (i.e. DO NOT USE on production data).

The program requires a start date from which to delete data, an amount to delete -- which should be equal to a chunk size for TimescaleDB, and the number of times to delete that amount of data. Our 100M row dataset begins on 2016-01-01 at midnight, so that is the start date we'll use along with 12-hour chunks. So, to delete the first 3 chunks we run:

timescaledb-benchmark-delete --db-name=benchmark --table=cpu_ts \
    --start="2016-01-01T00:00:00Z" --amount="12h" --limit=3

This will print out the command used and time it took to execute in milliseconds:

SELECT drop_chunks('2016-01-01T12:00:00Z'::TIMESTAMPTZ, 'cpu_ts')
66ms

SELECT drop_chunks('2016-01-02T00:00:00Z'::TIMESTAMPTZ, 'cpu_ts')
19ms

SELECT drop_chunks('2016-01-02T12:00:00Z'::TIMESTAMPTZ, 'cpu_ts')
19ms

To benchmark the equivalent scenario on PostgreSQL requires you to disable the use of drop_chunks():

timescaledb-benchmark-delete --db-name=benchmark --table=cpu_pg \
    --start="2016-01-01T00:00:00Z" --amount="12h" --limit=3 \
    --use-drop-chunks=false
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