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How to Import CSV Data into PostgreSQL

· Java Zone

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Introduction

Many database servers support CSV data transfers and this post will show one way you can import CSV files to PostgreSQL.

SQL aggregation rocks!

My previous post demonstrated FlexyPool metrics capabilities and all connection related statistics were exported in CSV format.

When it comes to aggregation tabular data SQL is at its best. If your database engine supports SQL:2003 windows functions you should definitely make use of this great feature.

Scripting flavors

For scripting I mostly rely on Python or Bash scripting. Python is powerful and expressive while Bash scripting doesn’t need too many dependencies, even on Windows.

Scripting time

These are the CSV files to be imported :

$ ls -1 *.csv
concurrentConnectionRequestsHistogram.csv
concurrentConnectionsHistogram.csv
connectionAcquireMillis.csv
connectionLeaseMillis.csv
maxPoolSizeHistogram.csv
overallConnectionAcquireMillis.csv
overflowPoolSizeHistogram.csv
retryAttemptsHistogram.csv

All these files are Codahale histogram and timer metrics and this is how the import script looks like:

#!/bin/bash
  
function import_histogram(){
    echo "Importing Histogram file: $2 to $1 table"
    psql metrics postgres <<SQL
        CREATE TABLE IF NOT EXISTS $1 (
            t BIGINT,
            count BIGINT,
            max NUMERIC(19, 6),
            mean NUMERIC(19, 6),
            min NUMERIC(19, 6),
            stddev NUMERIC(19, 6),
            p50 NUMERIC(19, 6),
            p75 NUMERIC(19, 6),
            p95 NUMERIC(19, 6),
            p98 NUMERIC(19, 6),
            p99 NUMERIC(19, 6),
            p999 NUMERIC(19, 6),
            PRIMARY KEY (t)
        );
        COPY $1(
            t,
            count,
            max,
            mean,
            min,
            stddev,
            p50,
            p75,
            p95,
            p98,
            p99,
            p999
        )
        FROM '$2' WITH DELIMITER ',' CSV HEADER;
SQL
}
  
function import_timer(){
    echo "Importing Timer file: $2 to $1 table"
    psql metrics postgres <<SQL
    CREATE TABLE IF NOT EXISTS $1 (
            t BIGINT,
            count BIGINT,
            max NUMERIC(19, 6),
            mean NUMERIC(19, 6),
            min NUMERIC(19, 6),
            stddev NUMERIC(19, 6),
            p50 NUMERIC(19, 6),
            p75 NUMERIC(19, 6),
            p95 NUMERIC(19, 6),
            p98 NUMERIC(19, 6),
            p99 NUMERIC(19, 6),
            p999 NUMERIC(19, 6),
            mean_rate NUMERIC(19, 6),
            m1_rate NUMERIC(19, 6),
            m5_rate NUMERIC(19, 6),
            m15_rate NUMERIC(19, 6),
            rate_unit VARCHAR(64),
            duration_unit VARCHAR(64),
            PRIMARY KEY (t)
        );
        COPY $1(
            t,
            count,
            max,
            mean,
            min,
            stddev,
            p50,
            p75,
            p95,
            p98,
            p99,
            p999,
            mean_rate,
            m1_rate,
            m5_rate,
            m15_rate,
            rate_unit,
            duration_unit
        )
        FROM '$2' WITH DELIMITER ',' CSV HEADER;       
SQL
}
  
for csv_file in *.csv
do
    table_name=`echo ${csv_file%%.*}|sed -e 's/\([A-Z]\)/_\L\1/g'`    
    csv_folder_path="$(cygpath -w `pwd`)"
    csv_file_path=$csv_folder_path/$csv_file   
    if [[ $table_name == *histogram ]]
    then
        import_histogram $table_name $csv_file_path   
    elif [[ $table_name == *millis ]]
    then
        import_timer $table_name $csv_file_path       
    fi
done

Because PostgreSQL requires Windows paths we need to use the $(cygpath -w `pwd`) command to translate the Cygwin like paths to their Windows equivalent.

Let’s run this scrip now:

vlad@HOME /cygdrive/d/metrics
$ dos2unix codahale_metrics_csv_to_postgres.sh
dos2unix: converting file codahale_metrics_csv_to_postgres.sh to Unix format ...
 
vlad@HOME /cygdrive/d/metrics
$ ./codahale_metrics_csv_to_postgres.sh
Importing Histogram file: D:\metrics/concurrentConnectionRequestsHistogram.csv to concurrent_connection_requests_histogram table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "concurrent_connection_requests_histogram_pkey" for table "concurrent_connection_requests_histogram"
CREATE TABLE
COPY 1537
Importing Histogram file: D:\metrics/concurrentConnectionsHistogram.csv to concurrent_connections_histogram table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "concurrent_connections_histogram_pkey" for table "concurrent_connections_histogram"
CREATE TABLE
COPY 1537
Importing Timer file: D:\metrics/connectionAcquireMillis.csv to connection_acquire_millis table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "connection_acquire_millis_pkey" for table "connection_acquire_millis"
CREATE TABLE
COPY 1537
Importing Timer file: D:\metrics/connectionLeaseMillis.csv to connection_lease_millis table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "connection_lease_millis_pkey" for table "connection_lease_millis"
CREATE TABLE
COPY 1537
Importing Histogram file: D:\metrics/maxPoolSizeHistogram.csv to max_pool_size_histogram table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "max_pool_size_histogram_pkey" for table "max_pool_size_histogram"
CREATE TABLE
COPY 1537
Importing Timer file: D:\metrics/overallConnectionAcquireMillis.csv to overall_connection_acquire_millis table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "overall_connection_acquire_millis_pkey" for table "overall_connection_acquire_millis"
CREATE TABLE
COPY 1537
Importing Histogram file: D:\metrics/overflowPoolSizeHistogram.csv to overflow_pool_size_histogram table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "overflow_pool_size_histogram_pkey" for table "overflow_pool_size_histogram"
CREATE TABLE
COPY 1537
Importing Histogram file: D:\metrics/retryAttemptsHistogram.csv to retry_attempts_histogram table
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "retry_attempts_histogram_pkey" for table "retry_attempts_histogram"
CREATE TABLE
COPY 1537

After running this script we got the following fully-loaded PostgreSQL tables:

codahale_csv_postgres_import

My next post will put window functions to work, as I want to compare the FLexyPool empirical metrics to the queueing theory probabilities.

If you have enjoyed reading my article and you’re looking forward to getting instant email notifications of my latest posts, you just need to follow my blog.


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Published at DZone with permission of Vlad Mihalcea, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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