{"id":11042,"date":"2018-03-23T09:53:06","date_gmt":"2018-03-23T08:53:06","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/what-is-the-maximum-in-list-size-in-postgresql\/"},"modified":"2018-03-23T09:53:06","modified_gmt":"2018-03-23T08:53:06","slug":"what-is-the-maximum-in-list-size-in-postgresql","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/what-is-the-maximum-in-list-size-in-postgresql\/","title":{"rendered":"What is the maximum in list size in PostgreSQL?"},"content":{"rendered":"<p>Yesterday, while being at a customer, an interesting question popped up: What is the maximum of in list values in PostgreSQL? I couldn&#8217;t answer although I never read somewhere that there is a limit. The following is for fun only and I am not saying that creating huge in lists is a good idea. Lets go.<\/p>\n<p><!--more--><\/p>\n<p>The version I tested is PostgreSQL 10:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres=# select version(), now();\n                                                  version                                                   |              now              \n------------------------------------------------------------------------------------------------------------+-------------------------------\n PostgreSQL 10.0 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16), 64-bit | 2018-03-21 18:29:50.269369+01\n(1 row)\n\npostgres=# create table t1 ( a varchar(10));\nCREATE TABLE\n<\/pre>\n<p>We will use a very simple bash script to build the in list and execute the result in PostgreSQL:<\/p>\n<pre class=\"brush: bash; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] cat t.sh \n#!\/bin\/bash\ncount=$1\n\nstatement='select * from t1 where a in ('\n\nfor (( i=1; i&lt;=$count; i++ ))\ndo  \n    if [ &quot;${i}&quot; -lt &quot;${count}&quot; ]; then\n        statement=&quot;${statement} &#039;${i}&#039;,&quot;\n    elif [ &quot;${i}&quot; == &quot;${count}&quot; ]; then\n        statement=&quot;${statement} &#039;${i}&#039;);&quot;\n    fi\ndone\n\npsql -c &quot;${statement}&quot; postgres\n<\/pre>\n<p>Lets start with 100:<\/p>\n<pre class=\"brush: bash; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] .\/t.sh 100\n a \n---\n(0 rows)\n\nTime: 0.983 ms\n<\/pre>\n<p>1000:<\/p>\n<pre class=\"brush: bash; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] .\/t.sh 1000\n a \n---\n(0 rows)\n\nTime: 1.525 ms\n<\/pre>\n<p>10000:<\/p>\n<pre class=\"brush: bash; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] .\/t.sh 10000\n a \n---\n(0 rows)\n\nTime: 11.549 ms\n<\/pre>\n<p>&#8230; takes a much longer (because of the bash script which fully occupies my virtual core):<\/p>\n<pre class=\"brush: bash; gutter: true; first-line: 1\">\n.\/t.sh: line 15: \/u01\/app\/postgres\/product\/10\/db_0\/bin\/psql: Argument list too long\n<\/pre>\n<p>So there at least is a limit with psql. Lets try by creating a sql script and execute that instead:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] cat t.sh \n#!\/bin\/bash\ncount=$1\n\necho 'select * from t1 where a in (' &gt; ttt.sql\n\nfor (( i=1; i&lt;=$count; i++ ))\ndo  \n    if [ &quot;${i}&quot; -lt &quot;${count}&quot; ]; then\n        echo  \"&#039;${i}&#039;,\" &gt;&gt; ttt.sql\n    elif [ &quot;${i}&quot; == &quot;${count}&quot; ]; then\n        echo \"&#039;${i}&#039;);&quot; &gt;&gt; ttt.sql\n    fi\ndone\n\npsql -f ttt.sql postgres\n<\/pre>\n<p>This way of stringing together the statement is much more efficient than building the list by concatenating everything into one variable. Does it still work?<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] .\/t.sh 100000\n a \n---\n(0 rows)\n\nTime: 155.986 ms\n<\/pre>\n<p>Not a problem, one more:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] .\/t.sh 1000000\n a \n---\n(0 rows)\n\nTime: 14211.766 ms (00:14.212)\n<\/pre>\n<p>Still works. So now we could say: lets stop, who in the world will pass one million values into an in list. On the other hand, lets have fun and double:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] .\/t.sh 2000000\n a \n---\n(0 rows)\n\nTime: 3993.091 ms (00:03.993)\n<\/pre>\n<p>One more:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres@pgbox:\/home\/postgres\/ [PG10] .\/t.sh 3000000\npsql:ttt.sql:3000001: ERROR:  out of memory\nDETAIL:  Failed on request of size 524288.\nTime: 3026.925 ms (00:03.027)\n<\/pre>\n<p>Ok, now I am hitting some limits, but probably not those of PostgreSQL. I&#8217;ll test further when I have more time for that \ud83d\ude42<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Yesterday, while being at a customer, an interesting question popped up: What is the maximum of in list values in PostgreSQL? I couldn&#8217;t answer although I never read somewhere that there is a limit. The following is for fun only and I am not saying that creating huge in lists is a good idea. Lets [&hellip;]<\/p>\n","protected":false},"author":28,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[229],"tags":[77],"type_dbi":[],"class_list":["post-11042","post","type-post","status-publish","format-standard","hentry","category-database-administration-monitoring","tag-postgresql"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v28.8 (Yoast SEO v28.8) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>What is the maximum in list size in PostgreSQL? - dbi Blog<\/title>\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.dbi-services.com\/blog\/what-is-the-maximum-in-list-size-in-postgresql\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What is the maximum in list size in PostgreSQL?\" \/>\n<meta property=\"og:description\" content=\"Yesterday, while being at a customer, an interesting question popped up: What is the maximum of in list values in PostgreSQL? 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