AlloyDB Select

Overview

You can use this Snap to fetch data from a database by providing a table name and configuring the connection. JSON paths can be used in a query and will have values from an incoming document substituted into the query. However, documents missing values for a specific JSON path will be written to Snap's error view.



Queries produced by this Snap have an equivalent format:
SELECT * FROM [table] WHERE [where clause] ORDER BY [ordering] LIMIT [limit] OFFSET [offset]

For more powerful functionality is desired, then use PostgreSQL - Execute Snap.

Known issues

When returning nonstandard types, the SQL statement will return a PGObject. You must use the Execute Snap in these cases.

Behavior changes

  • The following are the behavior changes caused by the JDBC driver upgrade for PostgreSQL Snap Pack and Google AlloyDB Snap Pack
  • Some error messages will now include the data type for certain values, for example:

    • Old: "...where (badId = 1) was aborted:..."

    • New: 
      "...where (badId = ('1'::numeric)) was
    aborted:..."
  • There are some minor text changes to a few of the error messages, for example:
    • Old: 
      "Hint: No operator matches the given name and argument
      types."
    • New: 
      "Hint: No operator matches the given name and argument
    type(s)."

Snap views

View Description Examples of upstream and downstream Snaps
Input This Snap has at most one document input view. If the input view is defined, then the where clause can substitute incoming values for a given expression (in for example, to use it as a lookup).
Output This Snap produces one document for each row in the table. After a query is executed, the query's results are merged into the incoming document, overwriting any existing keys' values. The original document is output if there are no results from the query.

A second view can be added to push the metadata for the table as a document. The metadata document can then be passed into the second input view of AlloyDB Insert Snap so that the table is created in AlloyDB with a similar schema as the source table.
Error

Error handling is a generic way to handle errors without losing data or failing the Snap execution. You can handle the errors that the Snap might encounter when running the pipeline by choosing one of the following options from the When errors occur list under the Views tab. The available options are:

  • Stop Pipeline Execution Stops the current pipeline execution when an error occurs.
  • Discard Error Data and Continue Ignores the error, discards that record, and continues with the remaining records.
  • Route Error Data to Error View Routes the error data to an error view without stopping the Snap execution.

Learn more about Error handling in Pipelines.

Snap settings

Legend:
  • Expression icon (): Allows using pipeline parameters to set field values dynamically (if enabled). SnapLogic Expressions are not supported. If disabled, you can provide a static value.
  • SnapGPT (): Generates SnapLogic Expressions based on natural language using SnapGPT. Learn more.
  • Suggestion icon (): Populates a list of values dynamically based on your Snap configuration. You can select only one attribute at a time using the icon. Type into the field if it supports a comma-separated list of values.
  • Upload : Uploads files. Learn more.
Learn more about the icons in the Snap settings dialog.
Field / Field set Type Description
Label String

Required. Specify a unique name for the Snap. Modify this to be more appropriate, especially if more than one of the same Snaps is in the pipeline.

Default value: AlloyDB Select

Example: Select Query
Schema name String/Expression/ Suggestion The database schema name. Selecting a schema filters the Table name list to show only those tables within the selected schema. The property is suggestible and will retrieve available database schemas during suggest values.

Default value: N/A

Example: SYS
Table name String/Expression/ Suggestion Required. Specify the name of the table to execute a select query on.

Default value: N/A

Example: People
Where clause String/Expression/ Suggestion Where clause of the select statement. This supports document value substitution (such as $person.firstname will be substituted with the value found in the incoming document at the path).
Warning: Caution

Using expressions that join strings together to create SQL queries or conditions has a potential SQL injection risk and therefore is unsafe. Ensure that you understand all implications and risks involved before using concatenation of strings with '=' Expression enabled.

Default value: N/A

Example:

Without using expressions
  • email = 'you@example.com' or email = $email

  • emp=$emp

Using expressions

  • "EMPNO=$EMPNO and ENAME=$EMPNAME"

  • "emp='" + $emp + "'"

  • "EMPNO=" + $EMPNO + " and ENAME='" + $EMPNAME+ "'"
Order By Enter the columns in the order in which you want to order by. The default database sort order will be used.
Limit offset Integer/Expression Number of rows to return from the query.

Default value: None.

Example: 10
Limit rows Integer/Expression Number of rows to return from the query.

Default value: None.

Example: 10
Output fields String/Expression/ Suggestion Enter or select output field names for the SQL SELECT statement. To select all fields, leave it at the default.

Default value: None.

Example: email, address, first, last, etc.
Fetch output fields In schema Checkbox Select this checkbox to include only the selected fields or columns in the Output Schema (second output view). If you do not provide any Output fields, all the columns are visible in the output.If you provide output fields, we recommend you select the Fetch Output Fields In Schema check box.

Default status: Deselected
Pass through Checkbox If checked, the input document will be passed through to the output view under the 'original' key.

Default status: Selected
Ignore empty result Checkbox If selected, no document will be written to the output view when a SELECT operation does not produce any result. If this property is not selected and the Pass through property is selected, the input document will be passed through to the output view.

Default status: Deselected
Auto commit Dropdown list Select one of the options for this property to override the state of the Auto commit property on the account. The Auto commit at the Snap-level has three values: True, False, and Use account setting. The expected functionality for these modes are:
  • True - The Snap will execute with autocommit enabled regardless of the value set for Auto commit in the Account used by the Snap.

  • False - The Snap will execute with auto-commit disabled regardless of the value set for Auto commit in the Account used by the Snap.

  • Use account setting - The Snap will execute with the Auto commit property value inherited by the Account used by the Snap.

Default value: False
Match data types Checkbox This property applies only when the Output fields property is provided with any field value.

If this property is selected, the Snap tries to match the output data types same as when the Output fields property is empty (SELECT * FROM ...). The output preview would be in the same format as the one when SELECT * FROM is implied and all the contents of the table are displayed.

Default status: Deselected
Number of retries Integer/Expression Specifies the maximum number of attempts to be made to receive a response. The request is terminated if the attempts do not result in a response.
Note: If the value is larger than 0, the Snap first downloads the target file into a temporary local file. If any error occurs during the download, the Snap waits for the time specified in the Retry interval and attempts to download the file again from the beginning. When the download is successful, the Snap streams the data from the temporary file to the downstream Pipeline. All temporary local files are deleted when they are no longer needed.

Ensure that the local drive has sufficient free disk space to store the temporary local file.

Default value: 0

Example: 3
Retry interval (seconds) Integer/Expression Specifies the time interval between two successive retry requests. A retry happens only when the previous attempt resulted in an exception.

Default value: 1

Example: 10
Staging mode Dropdown list Required when the value in the Number of retries field is greater than 0.
Specify the location to store input documents between retries, from the following options:

  • In memory: The query results are stored in the Snaplex memory. If the query is too large to fit in the memory space, it may cause the Snap to fail, so choose the On disk option.

  • On disk: The query results are stored on the disk in a temporary (tmp) directory that is managed by the SnapLogic platform. This directory is deleted automatically when the Snap terminates.

To disable staging, enter 0 in the Number of retries field.
Snap execution Dropdown list
Choose one of the three modes in which the Snap executes. Available options are:
  • Validate & Execute: Performs limited execution of the Snap and generates a data preview during pipeline validation. Subsequently, performs full execution of the Snap (unlimited records) during pipeline runtime.
  • Execute only: Performs full execution of the Snap during pipeline execution without generating preview data.
  • Disabled: Disables the Snap and all Snaps that are downstream from it.

Default value: Execute only

Example: Validate & Execute