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A package to enable easy data validation

Project description

Data Validation Tool

The Data Validation Tool (DVT) is an open sourced Python CLI tool based on the Ibis framework that compares heterogeneous data source tables with multi-leveled validation functions.

Data validation is a critical step in a Data Warehouse, Database or Data Lake migration project, where structured or semi-structured data from both the source and the destination tables are compared to ensure they are matched and correct after each migration step (e.g. data and schema migration, SQL script translation, ETL migration, etc.). The Data Validation Tool provides an automated and repeatable solution to perform this task.

DVT supports the following validation types:

  • Table level

    • Table row count
    • Group by row count
    • Column aggregation
    • Filters and limits
  • Column level

    • Full column data type
    • Selected column data type
  • Row level hash comparison (BigQuery tables only)

  • Schema validation

  • Raw SQL exploration

    • Run custom queries on different data sources

Installation

The installation page describes the prerequisites and setup steps needed to install and use the data validation tool.

Usage

Before using this tool, you will need to create connections to the source and target tables. Once the connections are created, you can run validations on those tables. Validation results can be printed to stdout (default) or outputted to BigQuery. The validation tool also allows you to save or edit validation configurations in a YAML file. This is useful for running common validations or updating the configuration.

Connections

The Connections page provides details about how to create and list connections for the validation tool.

Running CLI Validations

The data validation CLI is a main interface to use this tool.

The CLI has several different commands which can be used to create and re-run validations.

The validation tool first expects connections to be created before running validations. To create connections please review the Connections page.

Once you have your connections set up, you are ready to run the validations.

Validation command syntax and options

data-validation run
  --type or -t TYPE  Type of Data Validation (Column, GroupedColumn, Row, Schema)
  --source-conn or -sc SOURCE_CONN
                        Source connection details
                        See: *Data Source Configurations* section for each data source
  --target-conn or -tc TARGET_CONN
                        Target connection details
                        See: *Connections* section for each data source
  --tables-list or -tbls SOURCE_SCHEMA.SOURCE_TABLE=TARGET_SCHEMA.TARGET_TABLE  
                        Comma separated list of tables in the form schema.table=target_schema.target_table 
                        Target schema name and table name are optional.
                        i.e 'bigquery-public-data.new_york_citibike.citibike_trips'
  --grouped-columns or -gc GROUPED_COLUMNS
                        Comma separated list of columns for Group By i.e col_a,col_b
                        (Optional) Only used in GroupedColumn validations
  --primary-keys or -pc PRIMARY_KEYS
                        Comma separated list of columns to use as primary keys
                        (Optional) Only use in Row validations 
  --count COLUMNS       Comma separated list of columns for count or * for all columns
  --sum COLUMNS         Comma separated list of columns for sum or * for all numeric
  --min COLUMNS         Comma separated list of columns for min or * for all numeric
  --max COLUMNS         Comma separated list of columns for max or * for all numeric
  --avg COLUMNS         Comma separated list of columns for avg or * for all numeric
  --bq-result-handler or -bqrh PROJECT_ID.DATASET.TABLE
                        (Optional) BigQuery destination for validation results. Defaults to stdout.
                        See: *Validation Reports* section
  --service-account or -sa PATH_TO_SA_KEY
                        (Optional) Service account to use for BigQuery result handler output.
  --filters SOURCE_FILTER:TARGET_FILTER
                        Colon spearated string values of source and target filters.
                        If target filter is not provided, the source filter will run on source and target tables.
                        See: *Filters* section
  --config-file or -c CONFIG_FILE
                        YAML Config File Path to be used for storing validations.
  --threshold or -th THRESHOLD
                        (Optional) Float value. Maximum pct_difference allowed for validation to be considered a success. Defaults to 0.0
  --labels or -l KEY1=VALUE1,KEY2=VALUE2
                        (Optional) Comma-separated key value pair labels for the run.
  --verbose or -v       Verbose logging will print queries executed

The default aggregation type is a 'COUNT *'. If no aggregation flag (i.e count, sum , min, etc.) is provided, the default aggregation will run.

The Examples page provides many examples of how a tool can used to run powerful validations without writing any queries.

Running Custom SQL Exploration

There are many occasions where you need to explore a data source while running validations. To avoid the need to open and install a new client, the CLI allows you to run custom queries.

data-validation query 
  --conn or -c CONN
          The connection name to be queried
  --query or -q QUERY
          The raw query to run against the supplied connection

Query Configurations

You can customize the configuration for any given validation by providing use case specific CLI arguments or editing the saved YAML configuration file.

For example, the following command creates a YAML file for the validation of the new_york_citibike table. data-validation run -t Column -sc bq -tc bq -tbls bigquery-public-data.new_york_citibike.citibike_trips -c citibike.yaml

Here is the generated YAML file named citibike.yaml:

result_handler: {}
source: bq target:
bq validations:
  - aggregates:
    - field_alias: count
      source_column: null
      target_column: null
      type: count
      filters: []
      labels: []
schema_name: bigquery-public-data.new_york_citibike
table_name: citibike_trips
target_schema_name: bigquery-public-data.new_york_citibike
target_table_name: citibike_trips type: Column

You can now edit the YAML file if, for example, the new_york_citibike table is stored in datasets that have different names in the source and target systems. Once the file is updated and saved, the following command runs the new validation:

data-validation run-config -c citibike.yaml

The Data Validation Tool exposes several components that can be stitched together to generate a wide range of queries

Aggregated Fields

Aggregate fields contain the SQL fields that you want to produce an aggregate for. Currently the functions COUNT(), AVG(), SUM(), MIN() and MAX() are supported.

Sample Aggregate Config

validations:
- aggregates:
    - field_alias: count
    source_column: null
    target_column: null
    type: count
    - field_alias: count__tripduration
    source_column: tripduration
    target_column: tripduration
    type: count
    - field_alias: sum__tripduration
    source_column: tripduration
    target_column: tripduration
    type: sum
  - field_alias: bit_xor__hashed_column
    source_column: hashed_column
    target_column: hashed_column
    type: bit_xor

Filters

Filters let you apply a WHERE statement to your validation query (ie. SELECT * FROM table WHERE created_at > 30 days ago AND region_id = 71;). The filter is written in the syntax of the given source.

Note that you are writing the query to execute, which does not have to match between source and target as long as the results can be expected to align. If the target filter is omitted, the source filter will run on both the source and target tables.

Grouped Columns

Grouped Columns contain the fields you want your aggregations to be broken out by, e.g. SELECT last_updated::DATE, COUNT(*) FROM my.table will produce a resultset that breaks down the count of rows per calendar date.

Calculated Fields

Sometimes direct comparisons are not feasible between databases due to differences in how particular data types may be handled. These differences can be resolved by applying functions to columns in the source query itself. Examples might include trimming whitespace from a string, converting strings to a single case to compare case insensitivity, or rounding numeric types to a significant figure.

Once a calculated field is defined, it can be referenced by other calculated fields at any "depth" or higher. Depth controls how many subqueries are executed in the resulting query. For example, with the following yaml config...

- calculated_fields:
    - field_alias: rtrim_col_a
      source_calculated_columns: ['col_a']
      target_calculated_columns: ['col_a']
      type: rtrim
      depth: 0 # generated off of a native column
    - field_alias: ltrim_col_a
      source_calculated_columns: ['col_b']
      target_calculated_columns: ['col_b']
      type: ltrim
      depth: 0 # generated off of a native column
    - field_alias: concat_col_a_col_b
      source_calculated_columns: ['rtrim_col_a', 'ltrim_col_b']
      target_calculated_columns: ['rtrim_col_a', 'ltrim_col_b']
      type: concat
      depth: 1 # calculated one query above

is equivalent to the following SQL query...

SELECT
  CONCAT(rtrim_col_a, rtrim_col_b) AS concat_col_a_col_b
FROM (
  SELECT
      RTRIM(col_a) AS rtrim_col_a
    , LTRIM(col_b) AS ltrim_col_b
  FROM my.table
  ) as table_0

Calculated fields can be used by aggregate fields to produce validations on calculated or sanitized raw data, such as calculating the aggregate hash of a table. For example the following yaml config...

validations:
- aggregates:
  - field_alias: xor__multi_statement_hash
    source_column: multi_statement_hash
    target_column: multi_statement_hash
    type: bit_xor
  calculated_fields:
  - field_alias: multi_statement_hash
    source_calculated_columns: [multi_statement_concat]
    target_calculated_columns: [multi_statement_concat]
    type: hash
    depth: 2
  - field_alias: multi_statement_concat
    source_calculated_columns: [calc_length_col_a,
                                calc_ifnull_col_b,
                                calc_rstrip_col_c,
                                calc_upper_col_d]
    target_calculated_columns: [calc_length_col_a,
                                calc_ifnull_col_b,
                                calc_rstrip_col_c,
                                calc_upper_col_d]
    type: concat
    depth: 1
  - field_alias: calc_length_col_a
    source_calculated_columns: [col_a]
    target_calculated_columns: [col_a]
    type: length
    depth: 0
  - field_alias: calc_ifnull_col_b
    source_calculated_columns: [col_b]
    target_calculated_columns: [col_b]
    type: ifnull
    depth: 0
  - field_alias: calc_rstrip_col_c
    source_calculated_columns: [col_c]
    target_calculated_columns: [col_c]
    type: rstrip
    depth: 0
  - field_alias: calc_upper_col_d
    source_calculated_columns: [col_d]
    target_calculated_columns: [col_d]
    type: upper
    depth: 0

is equivalent to the following SQL query...

SELECT
  BIT_XOR(multi_statement_hash) AS xor__multi_statement_hash
FROM (
  SELECT
    FARM_FINGERPRINT(mult_statement_concat) AS multi_statement_hash
  FROM (
    SELECT
      CONCAT(calc_length_col_a,
             calc_ifnull_col_b,
             calc_rstrip_col_c,
             calc_upper_col_d) AS multi_statement_concat
    FROM (
      SELECT
          CAST(LENGTH(col_a) AS STRING) AS calc_length_col_a
        , IFNULL(col_b,
                 'DEFAULT_REPLACEMENT_STRING') AS calc_ifnull_col_b
        , RTRIM(col_c) AS calc_rstrip_col_c
        , UPPER(col_d) AS calc_upper_col_d
      FROM my.table
      ) AS table_0
    ) AS table_1
  ) AS table_2

Validation Reports

The data validation tool can write the results of a validation run to Google BigQuery or print to Std Out.

The output handlers tell the data validation where to store the results of each validation. By default the handler will print to stdout.

Configure tool to output to BigQuery

data-validation run 
  -t Column 
  -sc bq_conn 
  -tc bq_conn 
  -tbls bigquery-public-data.new_york_citibike.citibike_trips 
  -bqrh project_id.dataset.table
  -sa service-acct@project.iam.gserviceaccount.com

Building Matched Table Lists

Creating the list of matched tables can be a hassle. We have added a feature which may help you to match all of the tables together between source and target. The find-tables tool:

  • Pulls all tables in the source (applying a supplied allowed-schemas filter)
  • Pulls all tables from the target
  • Uses Levenshtein distance to match tables
  • Finally, it prints a JSON list of tables which can be a reference for the validation run config.

data-validation find-tables --source-conn source --target-conn target --allowed-schemas pso_data_validator

Add Support for an existing Ibis Data Source

If you want to add an Ibis Data Source which exists, but was not yet supported in the Data Validation tool, it is a simple process.

  1. In data_validation/data_validation.py

    • Import the extened Client for the given source (ie. from ibis.sql.mysql.client import MySQLClient).
    • Add the "<RefName>": Client to the global CLIENT_LOOKUP dictionary.
  2. In third_party/ibis/ibis_addon/operations.py

    • Add the RawSQL operator to the data source registry (for custom filter support).
  3. You are done, you can reference the data source via the config.

    • Config: {"source_type": "<RefName>", ...KV Values required in Client...}

Deploy to Composer

#!/bin/bash

export COMPOSER_ENV=""
export LOCATION=""

echo "Creating Composer Env: $COMPOSER_ENV"
gcloud services enable composer.googleapis.com
gcloud composer environments create $COMPOSER_ENV --location=$LOCATION --python-version=3

echo "Updating Composer Env Reqs: $COMPOSER_ENV"
# Composer builds Pandas and BigQuery for you, these should be stripped out
cat requirements.txt | grep -v pandas | grep -v google-cloud-bigquery > temp_reqs.txt
gcloud composer environments update $COMPOSER_ENV --location=$LOCATION --update-pypi-packages-from-file=temp_reqs.txt
rm temp_reqs.txt

# Deploy Package to Composer (the hacky way)
echo "Rebuilding Data Validation Package in GCS"
export GCS_BUCKET_PATH=$(gcloud composer environments describe $COMPOSER_ENV --location=$LOCATION | grep dagGcsPrefix | awk '{print $2;}')
gsutil rm -r $GCS_BUCKET_PATH/data_validation
gsutil cp -r data_validation $GCS_BUCKET_PATH/data_validation

# Deploy Test DAG to Composer
echo "Pushing Data Validation Test Operator to GCS"
gsutil cp tests/test_data_validation_operators.py $GCS_BUCKET_PATH/

Contributing

Contributions are welcome. See the contributing guide for details.

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