Zack Zack - 1 month ago 43
Python Question

Escaping special characters in elasticsearch

I am using the elasticsearch python client to make some queries to the elasticsearch instance that we are hosting.

I noticed that some characters need to be escaped. Specifically, these...

+ - && || ! ( ) { } [ ] ^ " ~ * ? : \


Is there a clean way to do this beyond what I've already got in mind? Surely there is a cleaner way than doing

term
.replace("+", "\+")
.replace("-", "\-")

# ....etc


I was hoping there was an API call that I could use, but I can't find one in the docs. This seems like a common enough issue that it should have been solved by someone.

Does anyone know the "correct" way of doing this?

EDIT : I am still not sure if there is an API call, but I got things concise enough to where I am happy.

def needs_escaping(character):

escape_chars = {
'\\' : True, '+' : True, '-' : True, '!' : True,
'(' : True, ')' : True, ':' : True, '^' : True,
'[' : True, ']': True, '\"' : True, '{' : True,
'}' : True, '~' : True, '*' : True, '?' : True,
'|' : True, '&' : True, '/' : True
}
return escape_chars.get(character, False)


sanitized = ''
for character in query:

if needs_escaping(character):
sanitized += '\\%s' % character
else:
sanitized += character

Answer

Yes, those characters will need to be replaced within content you want to search in a query_string query. To do that (assuming you are using PyLucene), you should be able to use QueryParserBase.escape(String).

Barring that, you could always adapt the QueryParserBase.escape source code to your needs:

public static String escape(String s) {
  StringBuilder sb = new StringBuilder();
  for (int i = 0; i < s.length(); i++) {
    char c = s.charAt(i);
    // These characters are part of the query syntax and must be escaped
    if (c == '\\' || c == '+' || c == '-' || c == '!' || c == '(' || c == ')' || c == ':'
      || c == '^' || c == '[' || c == ']' || c == '\"' || c == '{' || c == '}' || c == '~'
      || c == '*' || c == '?' || c == '|' || c == '&' || c == '/') {
      sb.append('\\');
    }
    sb.append(c);
  }
  return sb.toString();
}
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