a76889b319
1. Avoid print large string in error log
If user load a unqualified large string, the all string will be saved in error log,
so the error log is too big that can not be shown be using `show load warnings on "url"`.
Err: `Got packet bigger than 'max_allowed_packet' bytes`
2. Remove duplicate help doc
Do not allow doc with same title, or error thrown when starting FE:
`java.lang.IllegalArgumentException: Multiple entries with same key:`
48 lines
1.2 KiB
Markdown
48 lines
1.2 KiB
Markdown
---
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{
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"title": "coalesce",
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"language": "zh-CN"
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}
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---
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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# coalesce
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## description
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### Syntax
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`coalesce(expr1, expr2, ...., expr_n))`
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返回参数中的第一个非空表达式（从左向右）
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## example
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```
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mysql> select coalesce(NULL, '1111', '0000');
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+--------------------------------+
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| coalesce(NULL, '1111', '0000') |
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+--------------------------------+
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| 1111 |
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+--------------------------------+
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```
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## keyword
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COALESCE
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