Database

Elastic Search DSL

FAQ

Redis 连接报 ‘Connection refused’

排查步骤：

确认 Redis pod 在运行：

kubectl -n storage get pods -l app.kubernetes.io/instance=redis-shared

确认 Service 端点正常：

kubectl -n storage get endpoints redis-shared-master

从客户端 pod 内测试连通：

kubectl exec -it <pod> -- redis-cli -h redis-shared-master.storage -a <password> ping

如果外部应用连不上，确认使用的是正确的 namespace：
```
redis-shared-master.storage.svc.cluster.local:6379
```

如果密码不对，从 secret 获取：

kubectl -n storage get secret redis-shared-credentials -o jsonpath='{.data.redis-password}' | base64 -d

PostgreSQL 连接报 ‘password authentication failed’

确认密码 secret 存在：

kubectl -n database get secret <app>-postgres-password -o jsonpath='{.data.password}' | base64 -d

如果密码改了，需要更新引用它的所有应用的 env。
PostgreSQL 默认只允许集群内访问。外部访问需要通过 NodePort 或 port-forward：
```
kubectl -n database port-forward svc/postgresql 5432:5432
```

Redis 如何清空所有数据

kubectl -n storage exec redis-shared-master-0 -- redis-cli -a <password> FLUSHALL
kubectl -n storage exec redis-shared-master-0 -- redis-cli -a <password> FLUSHDB

⚠️ FLUSHALL 默认已被禁用（disableCommands: [FLUSHDB, FLUSHALL]）。如需使用，临时移除 disableCommands 后重建 Redis。

查看 Redis 内存使用和 key 数量

kubectl -n storage exec redis-shared-master-0 -- redis-cli -a <password> INFO memory
kubectl -n storage exec redis-shared-master-0 -- redis-cli -a <password> DBSIZE
kubectl -n storage exec redis-shared-master-0 -- redis-cli -a <password> INFO stats

PostgreSQL 数据库备份和恢复

# 备份
kubectl -n database exec deployment/postgresql -- \
  pg_dump -U postgres <database> > backup.sql

# 恢复
cat backup.sql | kubectl -n database exec -i deployment/postgresql -- \
  psql -U postgres <database>

Elastic Search DSL

Basic Query

exist query

Returns documents that contain an indexed value for a field.

GET /_search
{
  "query": {
    "exists": {
      "field": "user"
    }
  }
}

The following search returns documents that are missing an indexed value for the user.id field.

GET /_search
{
  "query": {
    "bool": {
      "must_not": {
        "exists": {
          "field": "user.id"
        }
      }
    }
  }
}

fuzz query

Returns documents that contain terms similar to the search term, as measured by a Levenshtein edit distance.

GET /_search
{
  "query": {
    "fuzzy": {
      "filed_A": {
        "value": "ki"
      }
    }
  }
}

Returns documents that contain terms similar to the search term, as measured by a Levenshtein edit distance.

GET /_search
{
  "query": {
    "fuzzy": {
      "filed_A": {
        "value": "ki",
        "fuzziness": "AUTO",
        "max_expansions": 50,
        "prefix_length": 0,
        "transpositions": true,
        "rewrite": "constant_score_blended"
      }
    }
  }
}

rewrite:

constant_score_boolean
constant_score_filter
top_terms_blended_freqs_N
top_terms_boost_N, top_terms_N
frequent_terms, score_delegating

ids query

Returns documents based on their IDs. This query uses document IDs stored in the _id field.

GET /_search
{
  "query": {
    "ids" : {
      "values" : ["2NTC5ZIBNLuBWC6V5_0Y"]
    }
  }
}

prefix query

The following search returns documents where the filed_A field contains a term that begins with ki.

GET /_search
{
  "query": {
    "prefix": {
      "filed_A": {
        "value": "ki",
         "rewrite": "constant_score_blended",
         "case_insensitive": true
      }
    }
  }
}

You can simplify the prefix query syntax by combining the <field> and value parameters.

GET /_search
{
  "query": {
    "prefix" : { "filed_A" : "ki" }
  }
}

range query

Returns documents that contain terms within a provided range.

GET /_search
{
  "query": {
    "range": {
      "filed_number": {
        "gte": 10,
        "lte": 20,
        "boost": 2.0
      }
    }
  }
}

GET /_search
{
  "query": {
    "range": {
      "filed_timestamp": {
        "time_zone": "+01:00",        
        "gte": "2020-01-01T00:00:00", 
        "lte": "now"                  
      }
    }
  }
}

regex query

Returns documents that contain terms matching a regular expression.

GET /_search
{
  "query": {
    "regexp": {
      "filed_A": {
        "value": "k.*y",
        "flags": "ALL",
        "case_insensitive": true,
        "max_determinized_states": 10000,
        "rewrite": "constant_score_blended"
      }
    }
  }
}

term query

Returns documents that contain an exact term in a provided field.

You can use the term query to find documents based on a precise value such as a price, a product ID, or a username.

GET /_search
{
  "query": {
    "term": {
      "filed_A": {
        "value": "kimchy",
        "boost": 1.0
      }
    }
  }
}

wildcard query

Returns documents that contain terms matching a wildcard pattern.

A wildcard operator is a placeholder that matches one or more characters. For example, the * wildcard operator matches zero or more characters. You can combine wildcard operators with other characters to create a wildcard pattern.

GET /_search
{
  "query": {
    "wildcard": {
      "filed_A": {
        "value": "ki*y",
        "boost": 1.0,
        "rewrite": "constant_score_blended"
      }
    }
  }
}

Database

FAQ

Subsections of Database

Elastic Search DSL

Basic Query