From 8272e103cb84fec65ba5d266582ecfb6ff386676 Mon Sep 17 00:00:00 2001 From: "dgrowley@gmail.com" Date: Wed, 31 Oct 2018 01:45:41 +1300 Subject: [PATCH v3] Add documentation section appendix detailing some limitations of PostgreSQL --- doc/src/sgml/dblimits.sgml | 125 +++++++++++++++++++++++++++++++++++++++++++++ doc/src/sgml/filelist.sgml | 1 + doc/src/sgml/postgres.sgml | 1 + 3 files changed, 127 insertions(+) create mode 100644 doc/src/sgml/dblimits.sgml diff --git a/doc/src/sgml/dblimits.sgml b/doc/src/sgml/dblimits.sgml new file mode 100644 index 0000000000..05634233ad --- /dev/null +++ b/doc/src/sgml/dblimits.sgml @@ -0,0 +1,125 @@ + + + + Database Limitations + + + The following table describes the limits of PostgreSQL + + + + <productname>PostgreSQL</productname> limitations + + + + Item + Limit + Comment + + + + + + Maximum Database Size + Unlimited + + + + + Maximum Number of Databases + Unlimited + + + + + Maximum Relation Size + 32 TB + Limited to 2^32 - 1 pages per relation. + + + + Maximum Columns per Table + 1600 + Further limited by tuple size fitting on a single page. See note below + + + + Maximum Field Size + 1 GB + + + + + Maximum Identifier Length + 63 characters + Can be increased by recompiling PostgreSQL + + + + Maximum Rows per Table + Unlimited + + + + + Maximum Indexes per Table + Unlimited + + + + + Maximum Indexed Columns + 32 + Can be increased by recompiling PostgreSQL. Limit includes + any INCLUDE columns + + + + Maximum Partition Keys + 32 + Can be increased by recompiling PostgreSQL + + + + Maximum Relations per Database + Unlimited + + + + + Maximum Partitions per Partitioned Relations + 268,435,456 + May be increased by using sub-partitioning + + + + +
+ + + + The maximum number of columns for a table is further reduced as the tuple + being stored must fit on a single heap page. Variable length fields such + as TEXT, VARCHAR and + CHAR can have their values stored out of line in the + table's TOAST table when the values are large enough to require it. Only + an 18 byte pointer must remain inside the tuple in the table's heap. For + shorter length variable length fields either a 4 byte or 1 byte field + header is used, and the value is stored inside the heap tuple. Often this + can mean the actual maximum number of columns that you can store inside a + table is further reduced as the tuple can become too large to fit inside a + single 8192 byte heap page. For example, excluding the tuple header, a + tuple made up of 1600 INT columns would consume 6400 bytes and could be + stored in a heap page, but a tuple of 1600 BIGINT columns would consume + 12800 bytes, therefore not fit inside a heap page. + + + + Columns which have been dropped from the table also contribute to the + maximum column limit, although the dropped column values for newly created + tuples are internally marked as NULL in the tuples null bitmap, which does + occupy space. + + + + diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml index 48ac14a838..be8d3d6800 100644 --- a/doc/src/sgml/filelist.sgml +++ b/doc/src/sgml/filelist.sgml @@ -185,6 +185,7 @@ + diff --git a/doc/src/sgml/postgres.sgml b/doc/src/sgml/postgres.sgml index 0070603fc3..369eca61cf 100644 --- a/doc/src/sgml/postgres.sgml +++ b/doc/src/sgml/postgres.sgml @@ -268,6 +268,7 @@ Appendixes &errcodes; + &dblimits; &datetime; &keywords; &features; -- 2.16.2.windows.1