{"id":3351,"date":"2024-03-13T06:51:29","date_gmt":"2024-03-13T06:51:29","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/"},"modified":"2025-07-30T14:57:44","modified_gmt":"2025-07-30T14:57:44","slug":"how-are-udf-and-udaf-defined-and-used-in-hive","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/","title":{"rendered":"How are UDF and UDAF defined and used in Hive?"},"content":{"rendered":"<p>In Hive, user-defined functions (UDFs) and user-defined aggregate functions (UDAFs) can be defined and implemented by writing Java code or using Hive&#8217;s custom function language (UDF\/UDAF).<\/p>\n<p>To define a UDF, you need to first write a Java class that inherits from Hive&#8217;s UDF class and implement the evaluate method. Then register this function in Hive using the CREATE FUNCTION statement.<\/p>\n<p>For example, here is a simple example of a UDF:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">import<\/span> org.apache.hadoop.hive.ql.exec.UDF;\r\n<span class=\"hljs-keyword\">import<\/span> org.apache.hadoop.io.Text;\r\n\r\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title class_\">MyUDF<\/span> <span class=\"hljs-keyword\">extends<\/span> <span class=\"hljs-title class_\">UDF<\/span> {\r\n  <span class=\"hljs-keyword\">public<\/span> Text <span class=\"hljs-title function_\">evaluate<\/span><span class=\"hljs-params\">(Text input)<\/span> {\r\n    <span class=\"hljs-keyword\">if<\/span> (input == <span class=\"hljs-literal\">null<\/span>) {\r\n      <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-literal\">null<\/span>;\r\n    }\r\n    <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">Text<\/span>(input.toString().toUpperCase());\r\n  }\r\n}\r\n<\/code><\/pre>\n<p>Next, register this UDF in Hive.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">FUNCTION<\/span> my_udf <span class=\"hljs-keyword\">AS<\/span> <span class=\"hljs-string\">'com.example.MyUDF'<\/span>;\r\n<\/code><\/pre>\n<p>To define a UDAF, you need to write a Java class that extends Hive&#8217;s UDAF class and implement the evaluate method to define the aggregation logic. Then register this aggregation function in Hive using the CREATE FUNCTION statement.<\/p>\n<p>For example, below is a simple example of a UDAF.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">import<\/span> org.apache.hadoop.hive.ql.exec.UDAF;\r\n<span class=\"hljs-keyword\">import<\/span> org.apache.hadoop.io.IntWritable;\r\n\r\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title class_\">MyUDAF<\/span> <span class=\"hljs-keyword\">extends<\/span> <span class=\"hljs-title class_\">UDAF<\/span> {\r\n  <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title class_\">MyUDAFEvaluator<\/span> <span class=\"hljs-keyword\">extends<\/span> <span class=\"hljs-title class_\">UDAFResolver2<\/span> {\r\n    <span class=\"hljs-keyword\">private<\/span> IntWritable result;\r\n\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-title function_\">MyUDAFEvaluator<\/span><span class=\"hljs-params\">()<\/span> {\r\n      reset();\r\n    }\r\n\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title function_\">reset<\/span><span class=\"hljs-params\">()<\/span> {\r\n      result = <span class=\"hljs-literal\">null<\/span>;\r\n    }\r\n\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-type\">boolean<\/span> <span class=\"hljs-title function_\">iterate<\/span><span class=\"hljs-params\">(IntWritable value)<\/span> {\r\n      <span class=\"hljs-keyword\">if<\/span> (value == <span class=\"hljs-literal\">null<\/span>) {\r\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-literal\">true<\/span>;\r\n      }\r\n      <span class=\"hljs-keyword\">if<\/span> (result == <span class=\"hljs-literal\">null<\/span>) {\r\n        result = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">IntWritable<\/span>(value.get());\r\n      } <span class=\"hljs-keyword\">else<\/span> {\r\n        result.set(result.get() + value.get());\r\n      }\r\n      <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-literal\">true<\/span>;\r\n    }\r\n\r\n    <span class=\"hljs-keyword\">public<\/span> IntWritable <span class=\"hljs-title function_\">terminatePartial<\/span><span class=\"hljs-params\">()<\/span> {\r\n      <span class=\"hljs-keyword\">return<\/span> result;\r\n    }\r\n\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-type\">boolean<\/span> <span class=\"hljs-title function_\">merge<\/span><span class=\"hljs-params\">(IntWritable other)<\/span> {\r\n      <span class=\"hljs-keyword\">if<\/span> (other == <span class=\"hljs-literal\">null<\/span>) {\r\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-literal\">true<\/span>;\r\n      }\r\n      <span class=\"hljs-keyword\">if<\/span> (result == <span class=\"hljs-literal\">null<\/span>) {\r\n        result = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">IntWritable<\/span>(other.get());\r\n      } <span class=\"hljs-keyword\">else<\/span> {\r\n        result.set(result.get() + other.get());\r\n      }\r\n      <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-literal\">true<\/span>;\r\n    }\r\n\r\n    <span class=\"hljs-keyword\">public<\/span> IntWritable <span class=\"hljs-title function_\">terminate<\/span><span class=\"hljs-params\">()<\/span> {\r\n      <span class=\"hljs-keyword\">return<\/span> result;\r\n    }\r\n  }\r\n}\r\n<\/code><\/pre>\n<p>Next, register this UDAF in Hive.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">FUNCTION<\/span> my_udaf <span class=\"hljs-keyword\">AS<\/span> <span class=\"hljs-string\">'com.example.MyUDAF'<\/span>;\r\n<\/code><\/pre>\n<p>Queries can be executed in Hive using predefined UDF and UDAF functions.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">SELECT<\/span> my_udf(column_name) <span class=\"hljs-keyword\">FROM<\/span> table_name;\r\n<span class=\"hljs-keyword\">SELECT<\/span> my_udaf(column_name) <span class=\"hljs-keyword\">FROM<\/span> table_name;\r\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>In Hive, user-defined functions (UDFs) and user-defined aggregate functions (UDAFs) can be defined and implemented by writing Java code or using Hive&#8217;s custom function language (UDF\/UDAF). To define a UDF, you need to first write a Java class that inherits from Hive&#8217;s UDF class and implement the evaluate method. Then register this function in Hive [&hellip;]<\/p>\n","protected":false},"author":10,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[453,1402,299,1404,1403],"class_list":["post-3351","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-development","tag-guide","tag-programming","tag-technology","tag-tutorial"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>How are UDF and UDAF defined and used in Hive? - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn about how are udf and udaf defined and used in hive?. Comprehensive guide with examples and best practices.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How are UDF and UDAF defined and used in Hive?\" \/>\n<meta property=\"og:description\" content=\"Learn about how are udf and udaf defined and used in hive?. Comprehensive guide with examples and best practices.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/\" \/>\n<meta property=\"og:site_name\" content=\"Blog - Silicon Cloud\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/SiliCloudGlobal\/\" \/>\n<meta property=\"article:published_time\" content=\"2024-03-13T06:51:29+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2025-07-30T14:57:44+00:00\" \/>\n<meta name=\"author\" content=\"Jackson Davis\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:site\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Jackson Davis\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/\"},\"author\":{\"name\":\"Jackson Davis\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/#\/schema\/person\/55a10b8b0457c35884c25677889ad350\"},\"headline\":\"How are UDF and UDAF defined and used in Hive?\",\"datePublished\":\"2024-03-13T06:51:29+00:00\",\"dateModified\":\"2025-07-30T14:57:44+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/\"},\"wordCount\":156,\"publisher\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/#organization\"},\"keywords\":[\"Development\",\"guide\",\"programming\",\"technology\",\"tutorial\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/\",\"url\":\"https:\/\/www.silicloud.com\/blog\/how-are-udf-and-udaf-defined-and-used-in-hive\/\",\"name\":\"How are UDF and UDAF defined and used in Hive? - Blog - Silicon Cloud\",\"isPartOf\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/#website\"},\"datePublished\":\"2024-03-13T06:51:29+00:00\",\"dateModified\":\"2025-07-30T14:57:44+00:00\",\"description\":\"Learn about how are udf and udaf defined and used in hive?. 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