Snowflake

Snowflake is a cloud data warehouse.

Prerequisite

• Ensure that your Dremio cluster is at version 23.1 or later.

Configuring Snowflake as a Source

1. In the bottom-left corner of the Datasets page, click Add Source.
2. Under Databases in the Add Data Source dialog, select Snowflake.

General

1. In the Name field, specify the name by which you want the Snowflake source to appear in the Databases section.

2. Under Connection, follow these steps:

   note

   The optional connection parameters are case-sensitive. For example, if the name of a warehouse uses upper case only (e.g., WAREHOUSE1), specify it the same way in the Warehouse field.

   1. In the Host field, specify the hostname of the Snowflake source in this format: LOCATOR_ID.snowflakecomputing.com.
   2. (Optional) In the Database field, specify the default database to use.
   3. (Optional) In the Role field, specify the default access-control role to use.
   4. (Optional) In the Schema field, specify the default schema to use.
   5. (Optional) In the Warehouse field, specify the warehouse that will provide resources for executing DML statements and queries.

3. Under Authentication, select one of these options:

   • No Authentication: Select this option if you want Dremio to connect to the database without authenticating.
   • Master Credentials: Select this option if you want Dremio to connect to the database by using a username and a password.

Advanced Options

On the Advanced Options page, you can set values for these non-required options:

Option	Description
Maximum Idle Connections	The total number of connections allowed to be idle at a given time. The default maximum idle connections is 8.
Connection Idle Time	The amount of time (in seconds) allowed for a connection to remain idle before the connection is terminated. The default connection idle time is 60 seconds.
Query Timeout	The amount of time (in seconds) allowed to wait for the results of a query. If this time expires, the connection being used is returned to an idle state.
Record Fetch Size	The maximum number of records to allow a single query to fetch. This setting prevents queries from using too many resources.

Reflection Refresh

On the Reflection Refresh page, set the policy that controls how often reflections are scheduled to be refreshed automatically, as well as the time limit after which reflections expire and are removed.

Option	Description
Never refresh	Select to prevent automatic reflection refresh, default is to automatically refresh.
Refresh every	How often to refresh reflections, specified in hours, days or weeks. This option is ignored if Never refresh is selected.
Never expire	Select to prevent reflections from expiring, default is to automatically expire after the time limit below.
Expire after	The time limit after which reflections expire and are removed from Dremio, specified in hours, days or weeks. This option is ignored if Never expire is selected.

Metadata

On the Metadata page, you can configure settings to refresh metadata and handle datasets.

Dataset Handling

These are the optional Dataset Handling parameters.

Parameter	Description
Remove dataset definitions if underlying data is unavailable	By default, Dremio removes dataset definitions if underlying data is unavailable. Useful when files are temporarily deleted and added back in the same location with new sets of files.

Metadata Refresh

These are the optional Metadata Refresh parameters:

• Dataset Discovery: The refresh interval for fetching top-level source object names such as databases and tables. Set the time interval using this parameter.

  Parameter	Description
  (Optional) Fetch every	You can choose to set the frequency to fetch object names in minutes, hours, days, or weeks. The default frequency to fetch object names is 1 hour.

• Dataset Details: The metadata that Dremio needs for query planning such as information required for fields, types, shards, statistics, and locality. These are the parameters to fetch the dataset information.

  Parameter	Description
  Fetch mode	You can choose to fetch only from queried datasets that are set by default. Dremio updates details for previously queried objects in a source. Fetching from all datasets is deprecated.
  Fetch every	You can choose to set the frequency to fetch dataset details in minutes, hours, days, or weeks. The default frequency to fetch dataset details is 1 hour.
  Expire after	You can choose to set the expiry time of dataset details in minutes, hours, days, or weeks. The default expiry time of dataset details is 3 hours.

Privileges

On the Privileges page, you can grant privileges to specific users or roles. See Access Controls for additional information about user privileges.

1. (Optional) For Privileges, enter the user name or role name that you want to grant access to and click the Add to Privileges button. The added user or role is displayed in the Users table.
2. (Optional) For the users or roles in the Users table, toggle the green checkmark for each privilege you want to grant on the Dremio source that is being created.
3. Click Save after setting the configuration.

Editing a Snowflake Source

To edit a Snowflake source:

1. In the Datasets UI, click External Sources at the bottom-left of the page. A list of sources is displayed.
2. Under the Action column, click the Settings (gear) icon for the source you want to edit. From the list of actions, click Edit Details. Alternatively, you can click the source and click the Settings (gear) icon of the source.
3. In the Edit Source dialog, you cannot edit the name. Editing other parameters is optional. For parameters and advanced options, see Configuring Snowflake as a Source.
4. Click Save.

Removing a Snowflake Source

To remove a Snowflake source, perform these steps:

1. In the Datasets UI, click External Sources at the bottom-left of the page. A list of sources is displayed.
2. Under the Action column, click the Settings (gear) icon for the source that you want to remove.
3. From the list of actions, click Remove Source. Confirm that you want to remove the source.

caution

Removing a source causes all downstream views dependent on objects in this source to break.

Upgrading from Dremio Hub's Community Snowflake Plugin

caution

Removing a Snowflake source will drop all tables in the source. If you have any reflections configured on tables or table-level ACLs (customized privileges) in your Snowflake sources, copy the details of those items before you remove any sources. After upgrading and re-adding your sources, you will need to recreate those reflections and ACLs.

Views are not affected by removing and re-adding Snowflake sources, provided the sources are re-added with the same names.

note

The community Snowflake plugin from Dremio Hub is not compatible with Dremio version 23.0 and later. You should use Dremio version 23.1 or later if you have Snowflake sources because it comes with an official Snowflake plugin.

If you are upgrading an older version of Dremio to version 23.1 or later, you must do the following:

1. Note the details of any reflections and ACLs configured on tables in Snowflake sources.

2. Remove your Snowflake sources from Dremio.

3. Remove the community Snowflake plugin and the existing Snowflake JDBC driver.

4. Upgrade Dremio to version 23.1 or later.

5. Add your Snowflake sources to Dremio with the same names.

6. Recreate any table-level reflections and ACLs on your Snowflake sources.

Predicate Pushdowns

Dremio delegates the execution of these expressions and functions to the database being queried, often dramatically improving query performance. It can also offload entire SQL queries that include one or more of these expressions and functions.

||, AND, OR
+, -, /, *
<=, <, >, >=, =, <>, !=
ABS
ADD_MONTHS
AVG
BETWEEN
CASE
CAST
CEIL
CEILING
CHARACTER_LENGTH
CHAR_LENGTH
COALESCE
CONCAT
COUNT
COUNT_DISTINCT
COUNT_DISTINCT_MULTI
COUNT_FUNCTIONS
COUNT_MULTI
COUNT_STAR
DATE_ADD
DATE_SUB
DATE_TRUNC
DATE_TRUNC_DAY
DATE_TRUNC_HOUR
DATE_TRUNC_MINUTE
DATE_TRUNC_MONTH
DATE_TRUNC_QUARTER
DATE_TRUNC_WEEK
DATE_TRUNC_YEAR
DAYOFMONTH
DAYOFWEEK
DAYOFYEAR
EXTRACT
FLOOR
ILIKE
IN
IS DISTINCT FROM
IS NOT DISTINCT FROM
IS NOT NULL
IS NULL
LAST_DAY
LEFT
LENGTH
LIKE
LOCATE
LOWER
LPAD
LTRIM
MAX
MEDIAN
MIN
MOD
NOT
PERCENT_CONT
PERCENT_DISC
PERCENT_RANK
POSITION
REGEXP_LIKE
REPLACE
REVERSE
RIGHT
ROUND
RPAD
RTRIM
SIGN
SQRT
STDDEV
STDDEV_POP
STDDEV_SAMP
SUBSTR
SUBSTRING
SUM
TO_CHAR
TO_DATE
TRIM
TRUNC
TRUNCATE
UPPER

Running Queries Directly on Snowflake Through Dremio

Dremio users can run pass queries through Dremio to run on Snowflake. Doing so can sometimes decrease query execution times. For more information, see Querying Relational-Database Sources Directly.