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Snap type:

Read

Description:

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 the 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 the Snap have an equivalent format:

Code Block
SELECT * FROM [table] WHERE [where clause] ORDER BY [ordering] LIMIT [limit] OFFSET [offset]

If more powerful functionality is desired, then the Execute Snap should be used.

Known issue: The SQL statement will return a PGObject when returning non-standard types. You must use the Execute Snap in these cases.

Note
Non-standard types include standard PostgreSQL extensions such as JSON or XML, types defined in third party extensions such as PostGIS, or types defined via CREATE TYPE color AS ENUM (RED, GREEN, BLUE).

Prerequisites:

[None]

Support and limitations:

Works in Ultra Pipelines.

Account:

This Snap uses account references created on the Accounts page of SnapLogic Manager to handle access to this endpoint. See Configuring PostgreSQL Accounts for information on setting up this type of account.

Views:

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 such as to use it as a lookup).

Output

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

This Snap has at most one error view and produces zero or more documents in the view.

Note
Because the Snap must report what is reported by the database, the Snap sends all records to the error view and no record to the output view. If you want to see accurate results for each row you must set the batch size to 1 and execute the pipeline.

Settings

Label

Required. The 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.

Schema name

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: [None]

Table name

Required. Name of the table to execute a select query on.

Example: people

Default value: [None]

Where clause

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).

Examples:

Without using expressions

EmpId = 12
email = 'you@example.com'

Using expressions

"EMPNO=$EMPNO and ENAME=$EMPNAME"
email = $email
emp=$emp
"emp='" + $emp + "'"
"EMPNO=" + $EMPNO + " and ENAME='" + $EMPNAME+ "'"

Warning

title	Caution

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

Order by: Column names

Enter in the columns in the order in which you want to order by. The default database sort order will be used.

Example:

name
email

Limit offset

Number of rows to return from the query.
Example: 10

Default value: [None]

Limit rows

Number of rows to return from the query.
Example: 10

Default value: [None]

Output fields

Enter or select output field names for SQL SELECT statement. To select all fields, leave it at default.

Example: email, address, first, last, etc.

Default value: [None]

Fetch Output Fields In Schema

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	Cassandra - Select
	Cassandra - Select
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Default value: Not selected

Pass through

If checked, the input document will be passed through to the output view under the key 'original'.

Default value: Selected

Ignore empty result

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 value: Not selected

Number of retries

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.

Info

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.

Example: 3

Default value: 0

Retry interval (seconds)

Specifies the time interval between two successive retry requests. A retry happens only when the previous attempt resulted in an exception.

Example: 10

Default value: 1

Auto commit

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 auto-commit 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 Auto commit property value inherited by the Account used by the Snap.

Default value: False

Match data types

Conditional. 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.

Default value: Not selected

Staging mode

Required when the value in the Number of retries field is greater than 0.

Specify the location from the following options to store input documents between retries:

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, 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.

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page	Anaplan Read

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Note

For the 'Suggest' in the Order by columns and the Output fields properties, the value of the Table name property should be an actual table name instead of an expression. If it is an expression, it will display an error message "Could not evaluate accessor: ..." when the 'Suggest' button is clicked. This is because, at the time the "Suggest" button is clicked, the input document is not available for the Snap to evaluate the expression in the Table name property. The input document is available to the Snap only during the preview or execution time.

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	PostgreSQL Snap Pack
	PostgreSQL Snap Pack
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