In this article
Overview
This Snap allows you to fetch data from a database by providing a table name and configuring the connection. The Snap produces the records from the database on its output view which can then be processed by a downstream Snap.
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 given JSON path will be written to Snap's error view. 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.
Queries produced by Snap have an equivalent format:
SELECT * FROM [table] WHERE [where clause] ORDER BY [ordering] LIMIT [limit] OFFSET [offset] |
If more powerful functionality is desired, then Execute Snap should be used.
Snap Type
AlloyDB Select Snap is a Read Snap.
Prerequisites
None.
Support for Ultra Pipelines
Works in Ultra Pipelines.
Limitations
None.
Known Issues
The SQL statement will return a PGObject when returning non-standard types. You must use Execute Snap in these cases.
Snap Views
Type | Format | Number of Views | Examples of Upstream and Downstream Snaps | Description |
---|---|---|---|---|
Input | Document |
| 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 such as to use it as a lookup). | |
Output | Document |
| This Snap has one output view by default and produces one document for each row in the table. A second view can be added to dump out the metadata for the table as a document. The metadata document can then be fed into the second input view of PostgreSQL Insert Snap so that the table is created in PsotgreSQL 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 while running the Pipeline by choosing one of the following options from the When errors occur list under the Views tab:
Learn more about Error handling in Pipelines. |
Snap Settings
Asterisk ( * ): Indicates a mandatory field.
Suggestion icon (): Indicates a list that is dynamically populated based on the configuration.
Expression icon ( ): Indicates the value is an expression (if enabled) or a static value (if disabled). Learn more about Using Expressions in SnapLogic.
Add icon ( ): Indicates that you can add fields in the fieldset.
Remove icon ( ): Indicates that you can remove fields from the fieldset.
Upload icon ( ): Indicates that you can upload files.
Field Name | Field Type | Field Dependency | Description | |
---|---|---|---|---|
Label* Default Value: AlloyDB Select | String | N/A | Specify a unique name for the Snap. | |
Schema name Default Value: N/A | String/Expression/Suggestion | N/A | 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. | |
Table name* Default Value: N/A | String/Expression/Suggestion | N/A | Specify the name of the table to execute a select query on. | |
Where clause Default Value: N/A Without using expressions
Using expressions
Caution Using expressions that join strings together to create SQL queries or conditions has a potential SQL injection risk and hence unsafe. Ensure that you understand all implications and risks involved before using concatenation of strings with '=' Expression enabled. | String/Expression/Suggestion | N/A | 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). | |
Order By | Enter in the columns in the order in which you want to order by. The default database sort order will be used.. | |||
Limit offset Default Value: None | Integer/Expression/Suggestion | N/A | Number of rows to return from the query. | |
Limit rows Default Value: None. | Integer/Expression/Suggestion | N/A | Number of rows to return from the query. | |
Output fields Default Value: None | String/Expression/Suggestion | N/A | Enter or select output field names for SQL SELECT statement. To select all fields, leave it at default. | |
Fetch output fields In schema Default Value: Not Selected | Checkbox | N/A | Select this check box 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. | |
Pass through Default Value: Selected | Checkbox | N/A | If checked, the input document will be passed through to the output view under the key 'original'. | |
Ignore empty result Default Value: Not Selected | Checkbox | N/A | 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. | |
Auto commit Default Value: False | Dropdown List | N/A | 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:
| |
Match data types Default Value: Not Selected | Checkbox | N/A | This property applies only when the Output fields property is provided with any field value(s). 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. | |
Number of retries Default Value: 0 | Integer/Expression | N/A | 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. No macro found named "retries" on page "File Reader" in space "SD". If you're experiencing issues please see our Troubleshooting Guide. | |
Retry interval (seconds) Default Value: 1 | Integer/Expression | N/A | Specifies the time interval between two successive retry requests. A retry happens only when the previous attempt resulted in an exception. | |
Staging mode Default Value: In memory | 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:
To disable staging, enter 0 in the Number of retries field. | |
Snap Execution Default Value: | Dropdown list | N/A | Select one of the following three modes in which the Snap executes:
|
Example
Download this Pipeline.
Downloads
Download and import the Pipeline into SnapLogic.
Configure Snap accounts, as applicable.
Provide Pipeline parameters, as applicable.