Painless语法
第一次快速使用
- 首先准备一些练习数据
PUT hockey/_bulk?refresh
{"index":{"_id":1}}
{"first":"johnny","last":"gaudreau","goals":[9,27,1],"assists":[17,46,0],"gp":[26,82,1],"born":"1993/08/13"}
{"index":{"_id":2}}
{"first":"sean","last":"monohan","goals":[7,54,26],"assists":[11,26,13],"gp":[26,82,82],"born":"1994/10/12"}
{"index":{"_id":3}}
{"first":"jiri","last":"hudler","goals":[5,34,36],"assists":[11,62,42],"gp":[24,80,79],"born":"1984/01/04"}
{"index":{"_id":4}}
{"first":"micheal","last":"frolik","goals":[4,6,15],"assists":[8,23,15],"gp":[26,82,82],"born":"1988/02/17"}
{"index":{"_id":5}}
{"first":"sam","last":"bennett","goals":[5,0,0],"assists":[8,1,0],"gp":[26,1,0],"born":"1996/06/20"}
{"index":{"_id":6}}
{"first":"dennis","last":"wideman","goals":[0,26,15],"assists":[11,30,24],"gp":[26,81,82],"born":"1983/03/20"}
{"index":{"_id":7}}
{"first":"david","last":"jones","goals":[7,19,5],"assists":[3,17,4],"gp":[26,45,34],"born":"1984/08/10"}
{"index":{"_id":8}}
{"first":"tj","last":"brodie","goals":[2,14,7],"assists":[8,42,30],"gp":[26,82,82],"born":"1990/06/07"}
{"index":{"_id":39}}
{"first":"mark","last":"giordano","goals":[6,30,15],"assists":[3,30,24],"gp":[26,60,63],"born":"1983/10/03"}
{"index":{"_id":10}}
{"first":"mikael","last":"backlund","goals":[3,15,13],"assists":[6,24,18],"gp":[26,82,82],"born":"1989/03/17"}
{"index":{"_id":11}}
{"first":"joe","last":"colborne","goals":[3,18,13],"assists":[6,20,24],"gp":[26,67,82],"born":"1990/01/30"}
- 通过painless获取文档数据
Document values can be accessed from a Map named doc.
For example, the following script calculates a player’s total goals. This example uses a strongly typed int and a for loop.
通过total 打分 排序返回
GET hockey/_search
{
"query": {
"function_score": {
"script_score": {
"script": {
"lang": "painless",
"source": """
int total = 0;
for (int i = 0; i < doc['goals'].length; ++i) {
total += doc['goals'][i];
}
return total;
"""
}
}
}
}
}
- The following example uses a Painless script to sort the players by their combined first and last names. The names are accessed using doc['first'].value and doc['last'].value.
GET hockey/_search
{
"query": {
"match_all": {}
},
"sort": {
"_script": {
"type": "string",
"order": "asc",
"script": {
"lang": "painless",
"source": "doc['first.keyword'].value + ' ' + doc['last.keyword'].value"
}
}
}
}
Missing values
doc['field'].value throws an exception if the field is missing in a document.
To check if a document is missing a value, you can call doc['field'].size() == 0.
Updating Fields with Painless
You can also easily update fields. You access the original source for a field as ctx._source.<field-name>.
First, let’s look at the source data for a player by submitting the following request:
GET hockey/_search
{
"query": {
"term": {
"_id": 1
}
}
}
To change player 1’s last name to hockey, simply set ctx._source.last to the new value:
POST hockey/_update/1
{
"script": {
"lang": "painless",
"source": "ctx._source.last = params.last",
"params": {
"last": "hockey"
}
}
}
You can also add fields to a document. For example, this script adds a new field that contains the player’s nickname, hockey.
POST hockey/_update/1
{
"script": {
"lang": "painless",
"source": """
ctx._source.last = params.last;
ctx._source.nick = params.nick
""",
"params": {
"last": "gaudreau",
"nick": "hockey"
}
}
}
删除字段
POST hockey/_update/1
{
"script": {
"lang": "painless",
"source": "ctx._source.remove(\"last\");"
}
}
Dates
Date fields are exposed as ZonedDateTime, so they support methods like getYear, getDayOfWeek or e.g. getting milliseconds since epoch with getMillis. To use these in a script, leave out the get prefix and continue with lowercasing the rest of the method name. For example, the following returns every hockey player’s birth year:
GET hockey/_search
{
"script_fields": {
"birth_year": {
"script": {
"source": "doc.born.value.year"
}
}
}
}
Regular expressions
Regexes are enabled by default as the Setting script.painless.regex.enabled has a new option, limited, the default. This defaults to using regular expressions but limiting the complexity of the regular expressions. Innocuous looking regexes can have staggering performance and stack depth behavior. But still, they remain an amazingly powerful tool. In addition, to limited, the setting can be set to true, as before, which enables regular expressions without limiting them.To enable them yourself set script.painless.regex.enabled: true in elasticsearch.yml.
Painless’s native support for regular expressions has syntax constructs:
-
/pattern/: Pattern literals create patterns. This is the only way to create a pattern in painless. The pattern inside the/'s are just Java regular expressions. See Pattern flags for more. -
=~: The find operator return aboolean,trueif a subsequence of the text matches,falseotherwise. -
==~: The match operator returns aboolean,trueif the text matches,falseif it doesn’t.
Using the find operator (=~) you can update all hockey players with "b" in their last name:
POST hockey/_update_by_query
{
"script": {
"lang": "painless",
"source": """
if (ctx._source.last =~ /b/) {
ctx._source.last += "matched";
} else {
ctx.op = "noop";
}
"""
}
}
Using the match operator (==~) you can update all the hockey players whose names start with a consonant and end with a vowel:
POST hockey/_update_by_query
{
"script": {
"lang": "painless",
"source": """
if (ctx._source.last ==~ /[^aeiou].*[aeiou]/) {
ctx._source.last += "matched";
} else {
ctx.op = "noop";
}
"""
}
}
You can use the Pattern.matcher directly to get a Matcher instance and remove all of the vowels in all of their last names:
POST hockey/_update_by_query
{
"script": {
"lang": "painless",
"source": "ctx._source.last = /[aeiou]/.matcher(ctx._source.last).replaceAll('')"
}
}
Matcher.replaceAll is just a call to Java’s Matcher's replaceAll method so it supports $1 and \1 for replacements:
POST hockey/_update_by_query
{
"script": {
"lang": "painless",
"source": "ctx._source.last = /n([aeiou])/.matcher(ctx._source.last).replaceAll('$1')"
}
}
If you need more control over replacements you can call replaceAll on a CharSequence with a Function<Matcher, String> that builds the replacement. This does not support $1 or \1 to access replacements because you already have a reference to the matcher and can get them with m.group(1).
Calling Matcher.find inside of the function that builds the replacement is rude and will likely break the replacement process.
This will make all of the vowels in the hockey player’s last names upper case:
POST hockey/_update_by_query
{
"script": {
"lang": "painless",
"source": """
ctx._source.last = ctx._source.last.replaceAll(/[aeiou]/, m ->
m.group().toUpperCase(Locale.ROOT))
"""
}
}
Or you can use the CharSequence.replaceFirst to make the first vowel in their last names upper case:
POST hockey/_update_by_query
{
"script": {
"lang": "painless",
"source": """
ctx._source.last = ctx._source.last.replaceFirst(/[aeiou]/, m ->
m.group().toUpperCase(Locale.ROOT))
"""
}
}
Note: all of the _update_by_query examples above could really do with a query to limit the data that they pull back. While you could use a script query it wouldn’t be as efficient as using any other query because script queries aren’t able to use the inverted index to limit the documents that they have to check.
