Problem:

1. In postgres v13, SIMILAR TO .. ESCAPE NULL explicitly returns null
2. Improper implementation of ESCAPE in PostgresToStringVisitor.java

Implementation

• Modified SIMILAR TO ... ESCAPE NULL to avoid explicit NULL returns in PostgreSQL v13
  -- In postgres v12 ESCAPE NULL
• Fixed usage of SIMILAR TO in the codebase

-- In previous version, visit function didn't append "ESCAPE" to the query.

public void visit(PostgresSimilarTo op) {
sb.append("(");
visit(op.getString());
sb.append(" SIMILAR TO ");
visit(op.getSimilarTo());
if (op.getEscapeCharacter() != null) {
visit(op.getEscapeCharacter());
}
sb.append(")");
}

• Add configuration parameters in RESET (TODO task)

Partially resolves #912

Reference : Postgres Release Notes v13