elasticsearch - 是否可以通过散列文档的其他字段来计算 _id 字段？

Question

像这样，在文档中有一个字段并对它进行散列(例如 md5)以生成 _id:

PUT index/doc/1?pretty
{
"name": "foo",
"_id": "hash(doc['name'])"
}

Answer 1

是的，您可以使用 ingest pipeline 来做到这一点。

首先，让我们定义一个带有 script processor 的管道，该管道将计算您的 _id 字段。由于 Painless 不提供任何哈希方法，因此下面的方法是 SHA1 的 Painless 实现，但您可以将其替换为您选择的任何其他哈希算法

PUT _ingest/pipeline/id-generator
{
  "description" : "This pipeline generates an ID based on the SHA1 hash of the name field",
  "processors" : [
    {
      "script": {
        "lang": "painless",
          "source": """
def hex(int num) {
  def hex_chr = "0123456789abcdef".toCharArray();  
  String str = "";  
  for(int j = 7; j >= 0; j--) 
    str += hex_chr[((num >> (j * 4)) & 15)];  
  return str;
}
def str2blks_SHA1(String str){ 
  int nblk = ((str.length() + 8) >> 6) + 1; 
  int[] blks = new int[nblk * 16]; 
  for(int a = 0; a < nblk * 16; a++) 
    blks[a] = 0;int i = 0;
  for(; i < str.length(); i++) 
    blks[i >> 2] |= str.codePointAt(i) << (24 - (i % 4) * 8); 
  blks[i >> 2] |= 128 << (24 - (i % 4) * 8);
  blks[nblk * 16 - 1] = str.length() * 8; 
  return blks;
}
def add(def x, def y){ 
  def lsw = (x & 65535) + (y & 65535); 
  def msw = (x >> 16) + (y >> 16) + (lsw >> 16); 
  return (msw << 16) | (lsw & 65535);
} 
def rol(def num, def cnt){ 
  return (num << cnt) | (num >>> (32 - cnt));
}
def ft(def t, def b, def c, def d){
  if(t < 20) return (b & c) | ((~b) & d);
  if(t < 40) return b ^ c ^ d;
  if(t < 60) return (b & c) | (b & d) | (c & d);
  return b ^ c ^ d;
}
def kt(def t){ 
  return (t < 20) ?  1518500249 : (t < 40) ?  1859775393 : (t < 60) ? -1894007588 : -899497514; 
}
def calcSHA1(def str){ 
  def x = str2blks_SHA1(str); 
  def w = new def[80]; 
  def a = 1732584193; 
  def b = -271733879; 
  def c = -1732584194; 
  def d =  271733878; 
  def e = -1009589776; 
  for(def i = 0; i < x.length; i = i + 16){
    def olda = a; 
    def oldb = b; 
    def oldc = c; 
    def oldd = d; 
    def olde = e; 
    for(def j = 0; j < 80; j++){
      if(j < 16) {
        w[j] = x[i + j];
      } else {
        w[j] = rol(w[j-3] ^ w[j-8] ^ w[j-14] ^ w[j-16], 1);
      } 
      def t = add(add(rol(a, 5), ft(j, b, c, d)), add(add(e, w[j]), kt(j))); 
      e = d; 
      d = c; 
      c = rol(b, 30); 
      b = a; 
      a = t; 
    }
    a = add(a, olda); 
    b = add(b, oldb); 
    c = add(c, oldc); 
    d = add(d, oldd); 
    e = add(e, olde); 
  } 
  return hex(a) + hex(b) + hex(c) + hex(d) + hex(e);
}

ctx._id = calcSHA1(ctx.name);
"""
      }
    }
  ]
}

然后您可以通过引用管道来简单地为文档建立索引，如下所示:

POST myindex/_doc?pipeline=id-generator
{
  "name": "John Doe"
}

结果:

{
    "_index": "myindex",
    "_type": "_doc",
    "_id": "ae6e4d1209f17b460503904fad297b31e9cf6362",
    "_score": 1,
    "_source": {
      "name": "John Doe"
    }
  }