Escape backslashes in PDODBMultiIngestor for MySQL LOAD DATA INFILE

[jtpalmer]

Description

Escape backslashes in data fields.

Motivation and Context

Backslashes must be escaped in data fields (see https://dev.mysql.com/doc/refman/5.5/en/load-data.html). Depending on what character directly follows the backslash a variety of issues arise. If a field contains only a backslash it escapes the enclosing character corrupting all data that follows.

Tests performed

Shredded and ingested data containing a backslash. Confirmed that the correct data was ingested.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project as found in the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[smgallo]

I will do the same in ETLv2.