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Snap type:

Write

Description:

This Snap allows you to execute arbitrary SQL.

Valid JSON paths that are defined in the where clause for queries/statements will be substituted with values from an incoming document. Documents will be written to the error view if the document is missing a value to be substituted into the query/statement.

If a select query is executed, the query's results are merged into the incoming document and any existing keys will have their values overwritten. On the other hand, the original document is written if there are no results from the query.

Note
You can drop your database with it, so be careful.

Prerequisites:

[None]

Support and limitations:

Works in Ultra Task Pipelines.
Does not support $$ as an escape character for enclosing string input, as $ is a reserved character for variable substitution in SnapLogic.

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 allows zero or one input views. If the input view is defined, then the where clause can substitute incoming values for a given expression.

Output

This Snap allows zero or one output view and produces documents in the view.

Error

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

Note
Database Write Snaps output all records of a batch (as configured in your account settings) to the error view if the write fails during batch processing.

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.

SQL statement

Required.Specifies the SQL statement to execute on the server.

There are two possible scenarios that you encounter when working with SQL statements in SnapLogic. You must understand the following scenarios to successfully execute your SQL statements:

Scenario 1: Executing SQL statements without expressions
If the expression toggle of the SQL statement field is not selected:

The SQL statement must not be within quotes.
The $<variable_name> parts of the SQL statement are expressions. In the below example, $id and $book.

Examples:

Multiexcerpt include macro

name	ME_DB_Execute_Snaps_Scenario1
page	Azure SQL - Execute

Additionally, the JSON path (e.g. $myName) is allowed only in the WHERE clause.

If the SQL statement starts with SELECT (case-insensitive), the Snap regards it as a select-type query and executes once per input document. If not, it regards it as write-type query and executes in batch mode.

Scenario 2: Executing SQL queries with expressions
If the expression toggle of the SQL statement field is selected:

The SQL statement must be within quotes.
The + $<variable_name> + parts of the SQL statement are expressions, and must not be within quotes. In the below example, $tablename.
The $<variable_name> parts of the SQL statement is bind parameter and must be within quotes. In the below example, $id and $book.

Note
Table name and column names must not be provided as bind parameters. Only values can be provided as bind parameters.

Examples:

Multiexcerpt include macro

name	ME_DB_Execute_Snaps_Scenario2
page	Azure SQL - Execute

Known issue: When the SQL statement property is an expression, the Pipeline parameters are shown in the suggest, but not the input schema.

Note
The non-expression form uses bind parameters, so it is much faster than executing N arbitrary SQL expressions.

Warning
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.

Known issue: The SQL statement will return a PGObject when returning non-standard types.

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). They can be converted to strings using CAST(x AS TEXT) where 'x' is the name of the column.
The '$' sign and identifier characters, such as double quotes (“), single quotes ('), or back quotes (`), are reserved characters and should not be used in comments or for purposes other than their originally intended purpose.

Warning

title	Single quotes in values must be escaped

Any relational database (RDBMS) treats single quotes (') as special symbols. So, single quotes in the data or values passed through a DML query may cause the Snap to fail when the query is executed. Ensure that you pass two consecutive single quotes in place of one within these values to escape the single quote through these queries.

For example:

If String	To pass this value	Use
Has no single quotes	Schaum Series	`'`Schaum Series`'`
Contains single quotes	`O'Reilly's Publication`	'`O''Reilly''s Publication`'

Default value: [None]

Pass through

If selected, the input document will be passed through to the output view under the key 'original'. This property applies only to the Execute Snaps with SELECT statement.

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.

Example: 3

Default value: 0

Multiexcerpt include macro

name	retries
page	File Reader

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: Use account setting

Note
'Auto commit' may be enabled for certain use cases if PostgreSQL jdbc driver is used in either Redshift, PostgreSQL or generic JDBC Snap. But the JDBC driver may cause out of memory issues when Select statements are executed. In those cases, “Auto commit" in Snap property should be set to ‘False’ and the Fetch size in the “Account setting" can be increased for optimal performance.

Multiexcerpt macro

name	DDL Auto Commit

Behavior of DML Queries in Database Execute Snap when auto-commit is falseDDL queries used in the Database Execute Snap will be committed by the Database itself, regardless of the Auto-commit setting.
When Auto commit is set to false for the DML queries, the commit is called at the end of the Snap's execution.
Instead of building multiple Snaps with inter dependent DML queries, it is recommended to use Stored Procedure and Multi Execute Snap.
The Auto commit needs to be true in a scenario where the downstream Snap does depend on the data processed on an Upstream Database Execute Snap containing a DML query.
When the Auto commit is set to the Use account setting on the Snap, the account level commit needs to be enabled.

Multiexcerpt include macro

name	Snap Execution
page	SOAP Execute

Multiexcerpt include macro

name	Execution_Detail_Write
page	SOAP Execute

Example

The following single-Snap Pipeline runs an SQL query containing a JOIN command to collate data between two PostgreSQL tables.

Download this Pipeline

Let us consider the following tables in a PostgreSQL DB. Notice that the column employee_id is common between these tables.

Table 1: AVemployees	Table 2: AVempsalary

The Snap accesses the PostgreSQL tables using a valid account and runs an SQL query that contains a JOIN command based on the following settings:

The output preview after executing this Pipeline displays the result for the SQL query.

Upon joining the two tables as defined in the SQL query, we can see the employee_id column in the second table is prefixed with its table name AVempsalary to differentiate it from the column with the same name in the AVemployees table. This is how the PostgreSQL - Execute Snap handles column with conflicting names in tables when the SQL statement contains a JOIN command.

Attachments

patterns	.slp, .zip

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	PostgreSQL Snap Pack
	PostgreSQL Snap Pack
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