ELT Aggregate
In this article
An account for the Snap
You must define an account for this Snap to communicate with your target CDW. Click the account specific to your target CDW below for more information:
Overview
Use this Snap to add aggregate functions such as COUNT, SUM, MIN, and MAX along with the GROUP BY clause in the incoming SQL query. GROUP BY clauses are used to group table records based on columns that contain classifying data and are optional in this Snap. This Snap also allows you to preview the result of the output query. You can validate the modified query using this preview functionality. The supported aggregate functions vary based on the account configuration. See the description of the Aggregate Function field in the Snap Settings section for details.
Prerequisites
None.
Limitations
- Only those columns that are referenced in this Snap are passed to the output. The rest are dropped.
- ELT Snap Pack does not support Legacy SQL dialect of Google BigQuery. We recommend that you use only the BigQuery's Standard SQL dialect in this Snap.
Known Issues
- If you define a HAVING predicate in the HAVING Predicate List field set of the ELT Aggregate Snap (to apply on the Snap’s output data), the Snap connected downstream of this ELT Aggregate Snap returns an error corresponding to this predicate during the Pipeline execution.
In any of the supported target databases, this Snap does not appropriately identify nor render column references beginning with an _ (underscore) inside SQL queries/statements that use the following constructs and contexts (the Snap works as expected in all other scenarios):
WHERE
clause (ELT Filter Snap)WHEN
clauseON
condition (ELT Join, ELT Merge Into Snaps)HAVING
clauseQUALIFY
clause- Insert expressions (column names and values in ELT Insert Select, ELT Load, and ELT Merge Into Snaps)
- Update expressions list (column names and values in ELT Merge Into Snap)
- Secondary
AND
condition Inside SQL query editor (ELT Select and ELT Execute Snaps)
Workaround
As a workaround while using these SQL query constructs, you can:
- Precede this Snap with an ELT Transform Snap to re-map the '_' column references to suitable column names (that do not begin with an _ ) and reference the new column names in the next Snap, as needed.
- In case of Databricks Lakehouse Platform where CSV files do not have a header (column names), a simple query like
SELECT * FROM CSV.`/mnt/csv1.csv`
returns default names such as _c0, _c1, _c2 for the columns which this Snap cannot interpret. To avoid this scenario, you can:- Write the data in the CSV file to a DLP table beforehand, as in:
CREATE TABLE csvdatatable (a1 int, b1 int,…) USING CSV `/mnt/csv1.csv`
where a1, b1, and so on are the new column names. - Then, read the data from this new table (with column names a1, b1, and so on) using a simple SELECT statement.
- Write the data in the CSV file to a DLP table beforehand, as in:
- In case of Databricks Lakehouse Platform, all ELT Snaps' preview data (during validation) contains a value with precision higher than that of the actual floating point value (float data type) stored in the Delta. For example, 24.123404659344 instead of 24.1234. However, the Snap reflects the exact values during Pipeline executions.
Due to an issue with Databricks Runtime Version 11 and above, the Snap fails to calculate the value for the linear regression aggregate function REGR_R2 for the target DLP instance and returns a cast exception. As a workaround, you can revert your Databricks Runtime Version to 10.5 or below.
When running without Sub-Query Pushdown Optimization (SPDO), ELT Pipelines that contain an ELT Aggregate Snap and configured with one or more GROUP BY ROLLUP fields, do not verify the column data types while inserting the Snap output values in the target table. This may lead to incorrect data written to the target table. However, as long as SPDO is on, the same Pipeline runs without this issue.
Snap Input and Output
Input/Output | Type of View | Number of Views | Examples of Upstream and Downstream Snaps | Description |
---|---|---|---|---|
Input | Document |
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| The SQL query in which to add the aggregate functions and the optional GROUP BY clause. |
Output | Document |
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| The modified SQL query with the aggregate functions and GROUP BY clause. |
Snap Settings
SQL Functions and Expressions for ELT
You can use the SQL Expressions and Functions supported for ELT to define your Snap or Account settings with the Expression symbol = enabled, where available. This list is common to all target CDWs supported. You can also use other expressions/functions that your target CDW supports.
Parameter Name | Data Type | Description | Default Value | Example | ||||||||||||
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Label | String | Specify a name for the Snap. You can modify this to be more specific, especially if you have more than one of the same Snap in your pipeline. | ELT Aggregate | Aggregate Revenue | ||||||||||||
Get preview data | Checkbox | Select this checkbox to include a preview of the query's output. The Snap performs limited execution and generates a data preview during Pipeline validation. In the case of ELT Pipelines, only the SQL query flows through the Snaps but not the actual source data. Hence, the preview data for a Snap is the result of executing the SQL query that the Snap has generated in the Pipeline. The number of records displayed in the preview (upon validation) is the smaller of the following:
Rendering Complex Data Types in Databricks Lakehouse Platform Based on the data types of the fields in the input schema, the Snap renders the complex data types like map and struct as object data type and array as an array data type. It renders all other incoming data types as-is except for the values in binary fields are displayed as a base64 encoded string and as string data type. | Not selected | Selected | ||||||||||||
General Aggregate Functions List | This field set enables you to specify the columns for which to add the aggregate functions. Each aggregate function must be specified as a new row. Click to add a row. This field set contains the following fields:
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Function* | String/Expression/Suggestion | Required. Select the aggregate function to use. Click to retrieve the list of the supported aggregate functions. The list displays the functions supported by the database that you select in the Account settings. An error is displayed if an account is not configured. See the Troubleshooting section for details. Alternatively, you can also enter the name of the aggregate function to use; you must, however, ensure that it is spelled correctly. Otherwise, the Snap displays an error. You can use the following aggregate functions:
Additionally, the following aggregate functions are available based on the database type:
See Snowflake Aggregate Functions, Redshift SQL Functions Reference, Aggregate Functions (Transact-SQL), Databricks Built-in Functions Reference, or BigQuery Aggregate Functions in Standard SQL for more information on the respective aggregate function. | N/A | AVG | ||||||||||||
Argument* | String/Expression | Required. Enter the field name or expression on which you want to apply the general aggregate function. | N/A | REVENUE | ||||||||||||
Eliminate duplicates | Check box | Select to apply DISTINCT to the column specified in the Field field. This means that the aggregate function is applied only to the unique values in the column. Behavior with COUNT_IF aggregate function Selecting this checkbox while using COUNT_IF aggregate function does not eliminate duplicate records in case of Snowflake and BigQuery databases, as there is no native support. However, it eliminates the duplicates from the list of records when used with a Redshift, Azure Synapse, or Databricks Lakehouse Platform (DLP) instance. | Not selected | Selected | ||||||||||||
Alias Name* | String | Required. Specify the column in which to display the result of the aggregate function. You can also reference this name in downstream Snaps to process the data further. | N/A | TOTAL_REVENUE | ||||||||||||
Linear Regression Aggregate Functions List | This field set enables you to specify the columns for which to apply the linear regression aggregate functions. Each function must be specified as a new row. Click to add a row. This field set contains the following fields:
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Function* | String/Expression/Suggestion | Required. Select the aggregate function to use. Click to retrieve the list of the supported linear regression aggregate functions. The list displays the functions supported by the database. An error is displayed if an account is not configured. See the Troubleshooting section for details. Alternatively, you can also enter the name of an aggregate function; you must, however, ensure that it is spelled correctly. Otherwise, the Snap displays an error. You can use the following aggregate functions:
See Snowflake Aggregate Functions, Databricks Built-in Functions Reference, or BigQuery Aggregate Functions in Standard SQL for more information on the respective aggregate function. Though not supported natively BigQuery does not natively support the above list of Linear Regression Aggregate Functions. However, SnapLogic provides you with the ability to use these functions with BigQuery through a series of internal query rewrites. | N/A | CORR | ||||||||||||
Argument 1* | String/Expression | Required. Enter the first field name or expression on which you want to apply the Aggregate function. | N/A | REVENUE_LOC1 | ||||||||||||
Argument 2* | String/Expression | Required. Enter the second field name or expression on which you want to apply the Aggregate function. | N/A | REVENUE_LOC2 | ||||||||||||
Alias Name* | String | Required. Specify the column in which to display the result of the aggregate function. You can also reference this name in downstream Snaps to process the data further. | N/A | LINREGAGG_REVENUE | ||||||||||||
Aggregate Concatenation Functions List (Not valid for Databricks Lakehouse Platform) | This field set enables you to specify the list of aggregate concatenation functions for aggregation. The list displays the functions supported by the database that you select in the Account settings. Each function must be specified as a new row. Click to add a row. This field set contains the following fields:
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Function* | String/Expression/Suggestion | Required. Select the aggregate concatenation function to use. Click to retrieve the list of the supported functions. The list displays the functions supported by the database that you select in the Account settings. An error is displayed if an account is not configured. See the Troubleshooting section for details. Alternatively, you can also enter the name of the aggregate concatenation function to use; you must, however, ensure that it is spelled correctly. Otherwise, the Snap displays an error. You can use the following aggregate functions:
See Snowflake Aggregate Functions, Redshift SQL Functions Reference, Aggregate Functions (Transact-SQL), or BigQuery Aggregate Functions in Standard SQL for more information on the respective aggregate function. | N/A | LISTAGG | ||||||||||||
Argument* | String/Expression | Required. Enter the field name or expression on which you want to apply the Aggregate Concatenation function. | N/A | NEW_LOCATIONS | ||||||||||||
Alias Name* | String | Required. Specify the column in which to display the result of the concatenation function. You can also reference this name in downstream Snaps to process the data further. | N/A | UNIQUE_LOCS_LIST | ||||||||||||
Delimiter | String/Expression | Specify the delimiting character (string constant) to be used to separate the concatenated values. | , (comma) | ; (semi-colon) | ||||||||||||
Percentile Distribution Functions List (Not valid for Azure Synapse, Databricks Lakehouse Platform, BigQuery) | This field set enables you to specify the list of percentile distribution functions to be used for aggregation. The list displays the functions supported by the database that you select in the Account settings. Each function must be specified as a new row. Click to add a row. This field set contains the following fields:
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Function* | String/Expression/Suggestion | Required. Select the percentile distribution function to use. Click to retrieve the list of the supported functions. The list displays the functions supported by the database that you select in the Account settings. An error is displayed if an account is not configured. See the Troubleshooting section for details. Alternatively, you can also enter the name of the percentile distribution function to use; you must, however, ensure that it is spelled correctly. Otherwise, the Snap displays an error. You can use the following aggregate functions:
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