Elasticsearch：全文搜索与分析

索引映射设计

import { Client } from '@elastic/elasticsearch';

const client = new Client({ node: 'http://localhost:9200' });

// 创建带有显式映射的索引
await client.indices.create({
  index: 'products',
  body: {
    settings: {
      number_of_shards: 3,
      number_of_replicas: 1,
      analysis: {
        analyzer: {
          product_analyzer: {
            type: 'custom',
            tokenizer: 'standard',
            filter: ['lowercase', 'stop', 'stemmer'],
          },
        },
      },
    },
    mappings: {
      properties: {
        id: { type: 'keyword' },
        name: {
          type: 'text',
          analyzer: 'product_analyzer',
          fields: {
            keyword: { type: 'keyword' },  // 用于排序/聚合
            suggest: { type: 'completion' }, // 用于自动补全
          },
        },
        description: { type: 'text', analyzer: 'product_analyzer' },
        price: { type: 'double' },
        category: { type: 'keyword' },
        tags: { type: 'keyword' },
        brand: { type: 'keyword' },
        inStock: { type: 'boolean' },
        rating: { type: 'float' },
        createdAt: { type: 'date' },
      },
    },
  },
});

全文搜索

// 基本的多字段搜索
const results = await client.search({
  index: 'products',
  body: {
    query: {
      multi_match: {
        query: 'wireless noise cancelling headphones',
        fields: ['name^3', 'description', 'tags^2'],  // 提升 name 和 tags 的权重
        type: 'best_fields',
        fuzziness: 'AUTO',   // 处理拼写错误
      },
    },
    highlight: {
      fields: { name: {}, description: { fragment_size: 150 } },
    },
    size: 20,
    from: 0,
  },
});

// 带过滤器的布尔查询
const filtered = await client.search({
  index: 'products',
  body: {
    query: {
      bool: {
        must: [
          { multi_match: { query: 'headphones', fields: ['name', 'description'] } },
        ],
        filter: [
          { term: { inStock: true } },
          { terms: { category: ['electronics', 'audio'] } },
          { range: { price: { gte: 50, lte: 500 } } },
          { range: { rating: { gte: 4.0 } } },
        ],
        should: [
          { term: { brand: 'Sony' } },  // 提升 Sony 产品的权重
        ],
        minimum_should_match: 0,
      },
    },
    sort: [
      { _score: { order: 'desc' } },
      { rating: { order: 'desc' } },
    ],
  },
});

用于分面搜索的聚合

const facets = await client.search({
  index: 'products',
  body: {
    query: { match: { name: 'headphones' } },
    aggs: {
      categories: {
        terms: { field: 'category', size: 10 },
      },
      brands: {
        terms: { field: 'brand', size: 10 },
      },
      price_ranges: {
        range: {
          field: 'price',
          ranges: [
            { key: 'under_50', to: 50 },
            { key: '50_to_200', from: 50, to: 200 },
            { key: '200_to_500', from: 200, to: 500 },
            { key: 'over_500', from: 500 },
          ],
        },
      },
      avg_rating: {
        avg: { field: 'rating' },
      },
      stats: {
        stats: { field: 'price' },
      },
    },
    size: 20,
  },
});

使用 Completion Suggester 实现自动补全

// 使用 completion 字段索引
const suggest = await client.search({
  index: 'products',
  body: {
    suggest: {
      product_suggest: {
        prefix: 'wireles',
        completion: {
          field: 'name.suggest',
          size: 5,
          fuzzy: { fuzziness: 1 },
        },
      },
    },
  },
});

const suggestions = suggest.suggest.product_suggest[0].options
  .map(o => ({ text: o.text, id: o._source.id }));

索引管理

# 检查集群健康状态
curl http://localhost:9200/_cluster/health?pretty

# 索引统计信息
curl http://localhost:9200/products/_stats?pretty

# 对读密集型索引进行强制合并
curl -X POST http://localhost:9200/products/_forcemerge?max_num_segments=1

# 索引生命周期管理 (ILM)
# 自动滚动大型索引

Elasticsearch 在全文搜索方面表现出色；对于简单用例，可以使用 PostgreSQL 的 tsvector。