Enable Holistics Canal

Closed Beta

Holistics Canal is now in Closed Beta!

If you are interested, please fill in this form and we will try to notify you with our new updates and Beta release! P.S. Make sure to mention the Database type that you would like Canal to support next. 😉

Knowledge Checkpoint

To learn about Holistics Canal, please head to this doc.

Supported Databases

Feature		PostgreSQL	Redshift	BigQuery	Snowflake
Supported		✅ Yes PostgreSQL >= 12 (not end-of-life)	✅ Yes	✅ Yes	✅ Yes
Connection Pooling		✅ Yes	✅ Yes	✅ Yes	✅ Yes
Parallel Download		❌ No	❌ No	❌ No	✅ Yes

Sub-features

Connection Pooling

When a "canal" (or connection) has been constructed between Holistics and your Data Warehouse, Holistics will try to re-use that same connection for multiple queries. Learn more

Parallel Download

Some databases provide a mechanism to download the result of a single query in multiple parts in parallel.
Note that this feature typically only makes a difference when your resultset has more than 5,000 rows.

Notes

Important Notes

Please make sure to read through these notes before enabling Holistics Canal.

Data Type Handling

Goals

The Goals of Canal Data Type Handling are:

• Precise: Data precision should be preserved as much as possible.
• Consumable: The data must be adequately readable by end-users and processible by Holistics post-processing.
• Efficient: The data must be stored and processed in efficient data structures so that they are fast to retrieve and process.

With the above goals in mind, below are some special data type handlings in Canal:

Number precision

• Floats: Canal supports upto 64-bit floating-point numbers.
• Decimals: For the "decimal" or "numeric" data types that have a fixed/arbitrary precision (non-floating precision), Canal supports upto decimal(38, 9).
  • For PostgreSQL and Redshift:
    • This means that a decimal number can only have upto 38 digits, including 29 whole digits and 9 fractional digits.
      • Numbers that have more than 29 whole digits will raise an error in Canal.
      • Numbers that have more than 9 fractional digits will be rounded to 9 fractional digits.
  • For BigQuery:
    • BIGDECIMAL and BIGNUMERIC data are cached are post-processed as text, meaning they can still be computed on your Data Warehouse and displayed to end-users, but Holistics won't be able to apply visual-level calculations to them.
  • Workarounds for decimals that are larger than decimal(38, 9):
    • Truncate/round to make them smaller: For example, instead of processing in meters, convert your data into kilometers. Canal only operates on the result of your data, so you can still perform big computations first, then convert the result to smaller numbers later before returning the query result.
    • Convert into text -> cannot apply numeric calculations but can still display them.
    • Convert into double (i.e. 64-bit float) -> lose some precision but can still display and apply numeric calculations.

Time precision

Holistics only process Time and Timestamp/Datetime values in upto microsecond precision. Values that have higher precisions will be rounded to microsecond precision.

We believe that microsecond precision is adequately precise and efficient for most analytical use cases. But please let us know if it does not suit your needs.

Database-specific Notes

PostgreSQL and Redshift

• Holistics Canal might still work with PostgreSQL < 12, but it is not guaranteed because PostgreSQL versions below 12 are end-of-life (ref).
• See Number precision above.

BigQuery

• When using Holistics Canal, your BigQuery queries on Holistics will always use GoogleSQL (formerly known as StandardSQL) instead of BigQuery's legacy syntax.
• See Number precision above.

Unsupported Databases:

• If you are using another database that is supported by Holistics but has not been supported by Holistics Canal, please let us know via this form.

What performance improvement can I expect when enabling Canal?

Canal typically speeds up Steps 4 and 5 of Holistics Report/Query Execution.

• It reduces the time between when the query is finished and the time the result is delivered to the end-users. In other words, it reduces Holistics latency in query executions.
• It does not make the Data Warehouse execute a query faster.
  • To optimize queries, please refer to this doc.

Below is an example comparison taken from our Community Post. Note that the query itself takes < 300ms to run in the database.

How to enable Holistics Canal

First, please register via this form and we will enable Holistics Canal in your workspace if applicable.

Then, in your Data Source settings, open Advanced Holistics Settings, check Enable Holistics Canal (and then Save it):

If you find any issues (typically with "Canal" in the error message), please reach out to Holistics Support.
In case it's urgent, please

1. Make sure to screenshot the error first
2. Disable Canal on your Data Source
3. Report the error (with screenshot) to Holistics Support

Note

Holistics Canal will be enabled by default in the future when it is stable.