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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>8.17. Range Types</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="rowtypes.html" title="8.16. Composite Types" /><link rel="next" href="domains.html" title="8.18. Domain Types" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">8.17. Range Types</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="rowtypes.html" title="8.16. Composite Types">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="datatype.html" title="Chapter 8. Data Types">Up</a></td><th width="60%" align="center">Chapter 8. Data Types</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="domains.html" title="8.18. Domain Types">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="RANGETYPES"><div class="titlepage"><div><div><h2 class="title" style="clear: both">8.17. Range Types</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-BUILTIN">8.17.1. Built-in Range Types</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-EXAMPLES">8.17.2. Examples</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-INCLUSIVITY">8.17.3. Inclusive and Exclusive Bounds</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-INFINITE">8.17.4. Infinite (Unbounded) Ranges</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-IO">8.17.5. Range Input/Output</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-CONSTRUCT">8.17.6. Constructing Ranges</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-DISCRETE">8.17.7. Discrete Range Types</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-DEFINING">8.17.8. Defining New Range Types</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-INDEXING">8.17.9. Indexing</a></span></dt><dt><span class="sect2"><a href="rangetypes.html#RANGETYPES-CONSTRAINT">8.17.10. Constraints on Ranges</a></span></dt></dl></div><a id="id-1.5.7.25.2" class="indexterm"></a><p>
Range types are data types representing a range of values of some
element type (called the range's <em class="firstterm">subtype</em>).
For instance, ranges
of <code class="type">timestamp</code> might be used to represent the ranges of
time that a meeting room is reserved. In this case the data type
is <code class="type">tsrange</code> (short for <span class="quote">“<span class="quote">timestamp range</span>”</span>),
and <code class="type">timestamp</code> is the subtype. The subtype must have
a total order so that it is well-defined whether element values are
within, before, or after a range of values.
</p><p>
Range types are useful because they represent many element values in a
single range value, and because concepts such as overlapping ranges can
be expressed clearly. The use of time and date ranges for scheduling
purposes is the clearest example; but price ranges, measurement
ranges from an instrument, and so forth can also be useful.
</p><div class="sect2" id="RANGETYPES-BUILTIN"><div class="titlepage"><div><div><h3 class="title">8.17.1. Built-in Range Types</h3></div></div></div><p>
PostgreSQL comes with the following built-in range types:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
<code class="type">int4range</code> — Range of <code class="type">integer</code>
</p></li><li class="listitem"><p>
<code class="type">int8range</code> — Range of <code class="type">bigint</code>
</p></li><li class="listitem"><p>
<code class="type">numrange</code> — Range of <code class="type">numeric</code>
</p></li><li class="listitem"><p>
<code class="type">tsrange</code> — Range of <code class="type">timestamp without time zone</code>
</p></li><li class="listitem"><p>
<code class="type">tstzrange</code> — Range of <code class="type">timestamp with time zone</code>
</p></li><li class="listitem"><p>
<code class="type">daterange</code> — Range of <code class="type">date</code>
</p></li></ul></div><p>
In addition, you can define your own range types;
see <a class="xref" href="sql-createtype.html" title="CREATE TYPE"><span class="refentrytitle">CREATE TYPE</span></a> for more information.
</p></div><div class="sect2" id="RANGETYPES-EXAMPLES"><div class="titlepage"><div><div><h3 class="title">8.17.2. Examples</h3></div></div></div><p>
</p><pre class="programlisting">
CREATE TABLE reservation (room int, during tsrange);
INSERT INTO reservation VALUES
(1108, '[2010-01-01 14:30, 2010-01-01 15:30)');
-- Containment
SELECT int4range(10, 20) @> 3;
-- Overlaps
SELECT numrange(11.1, 22.2) && numrange(20.0, 30.0);
-- Extract the upper bound
SELECT upper(int8range(15, 25));
-- Compute the intersection
SELECT int4range(10, 20) * int4range(15, 25);
-- Is the range empty?
SELECT isempty(numrange(1, 5));
</pre><p>
See <a class="xref" href="functions-range.html#RANGE-OPERATORS-TABLE" title="Table 9.50. Range Operators">Table 9.50</a>
and <a class="xref" href="functions-range.html#RANGE-FUNCTIONS-TABLE" title="Table 9.51. Range Functions">Table 9.51</a> for complete lists of
operators and functions on range types.
</p></div><div class="sect2" id="RANGETYPES-INCLUSIVITY"><div class="titlepage"><div><div><h3 class="title">8.17.3. Inclusive and Exclusive Bounds</h3></div></div></div><p>
Every non-empty range has two bounds, the lower bound and the upper
bound. All points between these values are included in the range. An
inclusive bound means that the boundary point itself is included in
the range as well, while an exclusive bound means that the boundary
point is not included in the range.
</p><p>
In the text form of a range, an inclusive lower bound is represented by
<span class="quote">“<span class="quote"><code class="literal">[</code></span>”</span> while an exclusive lower bound is
represented by <span class="quote">“<span class="quote"><code class="literal">(</code></span>”</span>. Likewise, an inclusive upper bound is represented by
<span class="quote">“<span class="quote"><code class="literal">]</code></span>”</span>, while an exclusive upper bound is
represented by <span class="quote">“<span class="quote"><code class="literal">)</code></span>”</span>.
(See <a class="xref" href="rangetypes.html#RANGETYPES-IO" title="8.17.5. Range Input/Output">Section 8.17.5</a> for more details.)
</p><p>
The functions <code class="literal">lower_inc</code>
and <code class="literal">upper_inc</code> test the inclusivity of the lower
and upper bounds of a range value, respectively.
</p></div><div class="sect2" id="RANGETYPES-INFINITE"><div class="titlepage"><div><div><h3 class="title">8.17.4. Infinite (Unbounded) Ranges</h3></div></div></div><p>
The lower bound of a range can be omitted, meaning that all points less
than the upper bound are included in the range. Likewise, if the upper
bound of the range is omitted, then all points greater than the lower bound
are included in the range. If both lower and upper bounds are omitted, all
values of the element type are considered to be in the range.
</p><p>
This is equivalent to considering that the lower bound is <span class="quote">“<span class="quote">minus
infinity</span>”</span>, or the upper bound is <span class="quote">“<span class="quote">plus infinity</span>”</span>,
respectively. But note that these infinite values are never values of
the range's element type, and can never be part of the range. (So there
is no such thing as an inclusive infinite bound — if you try to
write one, it will automatically be converted to an exclusive bound.)
</p><p>
Also, some element types have a notion of <span class="quote">“<span class="quote">infinity</span>”</span>, but that
is just another value so far as the range type mechanisms are concerned.
For example, in timestamp ranges, <code class="literal">[today,]</code> means the same
thing as <code class="literal">[today,)</code>. But <code class="literal">[today,infinity]</code> means
something different from <code class="literal">[today,infinity)</code> — the latter
excludes the special <code class="type">timestamp</code> value <code class="literal">infinity</code>.
</p><p>
The functions <code class="literal">lower_inf</code>
and <code class="literal">upper_inf</code> test for infinite lower
and upper bounds of a range, respectively.
</p></div><div class="sect2" id="RANGETYPES-IO"><div class="titlepage"><div><div><h3 class="title">8.17.5. Range Input/Output</h3></div></div></div><p>
The input for a range value must follow one of the following patterns:
</p><pre class="synopsis">
(<em class="replaceable"><code>lower-bound</code></em>,<em class="replaceable"><code>upper-bound</code></em>)
(<em class="replaceable"><code>lower-bound</code></em>,<em class="replaceable"><code>upper-bound</code></em>]
[<em class="replaceable"><code>lower-bound</code></em>,<em class="replaceable"><code>upper-bound</code></em>)
[<em class="replaceable"><code>lower-bound</code></em>,<em class="replaceable"><code>upper-bound</code></em>]
empty
</pre><p>
The parentheses or brackets indicate whether the lower and upper bounds
are exclusive or inclusive, as described previously.
Notice that the final pattern is <code class="literal">empty</code>, which
represents an empty range (a range that contains no points).
</p><p>
The <em class="replaceable"><code>lower-bound</code></em> may be either a string
that is valid input for the subtype, or empty to indicate no
lower bound. Likewise, <em class="replaceable"><code>upper-bound</code></em> may be
either a string that is valid input for the subtype, or empty to
indicate no upper bound.
</p><p>
Each bound value can be quoted using <code class="literal">"</code> (double quote)
characters. This is necessary if the bound value contains parentheses,
brackets, commas, double quotes, or backslashes, since these characters
would otherwise be taken as part of the range syntax. To put a double
quote or backslash in a quoted bound value, precede it with a
backslash. (Also, a pair of double quotes within a double-quoted bound
value is taken to represent a double quote character, analogously to the
rules for single quotes in SQL literal strings.) Alternatively, you can
avoid quoting and use backslash-escaping to protect all data characters
that would otherwise be taken as range syntax. Also, to write a bound
value that is an empty string, write <code class="literal">""</code>, since writing
nothing means an infinite bound.
</p><p>
Whitespace is allowed before and after the range value, but any whitespace
between the parentheses or brackets is taken as part of the lower or upper
bound value. (Depending on the element type, it might or might not be
significant.)
</p><div class="note"><h3 class="title">Note</h3><p>
These rules are very similar to those for writing field values in
composite-type literals. See <a class="xref" href="rowtypes.html#ROWTYPES-IO-SYNTAX" title="8.16.6. Composite Type Input and Output Syntax">Section 8.16.6</a> for
additional commentary.
</p></div><p>
Examples:
</p><pre class="programlisting">
-- includes 3, does not include 7, and does include all points in between
SELECT '[3,7)'::int4range;
-- does not include either 3 or 7, but includes all points in between
SELECT '(3,7)'::int4range;
-- includes only the single point 4
SELECT '[4,4]'::int4range;
-- includes no points (and will be normalized to 'empty')
SELECT '[4,4)'::int4range;
</pre><p>
</p></div><div class="sect2" id="RANGETYPES-CONSTRUCT"><div class="titlepage"><div><div><h3 class="title">8.17.6. Constructing Ranges</h3></div></div></div><p>
Each range type has a constructor function with the same name as the range
type. Using the constructor function is frequently more convenient than
writing a range literal constant, since it avoids the need for extra
quoting of the bound values. The constructor function
accepts two or three arguments. The two-argument form constructs a range
in standard form (lower bound inclusive, upper bound exclusive), while
the three-argument form constructs a range with bounds of the form
specified by the third argument.
The third argument must be one of the strings
<span class="quote">“<span class="quote"><code class="literal">()</code></span>”</span>,
<span class="quote">“<span class="quote"><code class="literal">(]</code></span>”</span>,
<span class="quote">“<span class="quote"><code class="literal">[)</code></span>”</span>, or
<span class="quote">“<span class="quote"><code class="literal">[]</code></span>”</span>.
For example:
</p><pre class="programlisting">
-- The full form is: lower bound, upper bound, and text argument indicating
-- inclusivity/exclusivity of bounds.
SELECT numrange(1.0, 14.0, '(]');
-- If the third argument is omitted, '[)' is assumed.
SELECT numrange(1.0, 14.0);
-- Although '(]' is specified here, on display the value will be converted to
-- canonical form, since int8range is a discrete range type (see below).
SELECT int8range(1, 14, '(]');
-- Using NULL for either bound causes the range to be unbounded on that side.
SELECT numrange(NULL, 2.2);
</pre><p>
</p></div><div class="sect2" id="RANGETYPES-DISCRETE"><div class="titlepage"><div><div><h3 class="title">8.17.7. Discrete Range Types</h3></div></div></div><p>
A discrete range is one whose element type has a well-defined
<span class="quote">“<span class="quote">step</span>”</span>, such as <code class="type">integer</code> or <code class="type">date</code>.
In these types two elements can be said to be adjacent, when there are
no valid values between them. This contrasts with continuous ranges,
where it's always (or almost always) possible to identify other element
values between two given values. For example, a range over the
<code class="type">numeric</code> type is continuous, as is a range over <code class="type">timestamp</code>.
(Even though <code class="type">timestamp</code> has limited precision, and so could
theoretically be treated as discrete, it's better to consider it continuous
since the step size is normally not of interest.)
</p><p>
Another way to think about a discrete range type is that there is a clear
idea of a <span class="quote">“<span class="quote">next</span>”</span> or <span class="quote">“<span class="quote">previous</span>”</span> value for each element value.
Knowing that, it is possible to convert between inclusive and exclusive
representations of a range's bounds, by choosing the next or previous
element value instead of the one originally given.
For example, in an integer range type <code class="literal">[4,8]</code> and
<code class="literal">(3,9)</code> denote the same set of values; but this would not be so
for a range over numeric.
</p><p>
A discrete range type should have a <em class="firstterm">canonicalization</em>
function that is aware of the desired step size for the element type.
The canonicalization function is charged with converting equivalent values
of the range type to have identical representations, in particular
consistently inclusive or exclusive bounds.
If a canonicalization function is not specified, then ranges with different
formatting will always be treated as unequal, even though they might
represent the same set of values in reality.
</p><p>
The built-in range types <code class="type">int4range</code>, <code class="type">int8range</code>,
and <code class="type">daterange</code> all use a canonical form that includes
the lower bound and excludes the upper bound; that is,
<code class="literal">[)</code>. User-defined range types can use other conventions,
however.
</p></div><div class="sect2" id="RANGETYPES-DEFINING"><div class="titlepage"><div><div><h3 class="title">8.17.8. Defining New Range Types</h3></div></div></div><p>
Users can define their own range types. The most common reason to do
this is to use ranges over subtypes not provided among the built-in
range types.
For example, to define a new range type of subtype <code class="type">float8</code>:
</p><pre class="programlisting">
CREATE TYPE floatrange AS RANGE (
subtype = float8,
subtype_diff = float8mi
);
SELECT '[1.234, 5.678]'::floatrange;
</pre><p>
Because <code class="type">float8</code> has no meaningful
<span class="quote">“<span class="quote">step</span>”</span>, we do not define a canonicalization
function in this example.
</p><p>
Defining your own range type also allows you to specify a different
subtype B-tree operator class or collation to use, so as to change the sort
ordering that determines which values fall into a given range.
</p><p>
If the subtype is considered to have discrete rather than continuous
values, the <code class="command">CREATE TYPE</code> command should specify a
<code class="literal">canonical</code> function.
The canonicalization function takes an input range value, and must return
an equivalent range value that may have different bounds and formatting.
The canonical output for two ranges that represent the same set of values,
for example the integer ranges <code class="literal">[1, 7]</code> and <code class="literal">[1,
8)</code>, must be identical. It doesn't matter which representation
you choose to be the canonical one, so long as two equivalent values with
different formattings are always mapped to the same value with the same
formatting. In addition to adjusting the inclusive/exclusive bounds
format, a canonicalization function might round off boundary values, in
case the desired step size is larger than what the subtype is capable of
storing. For instance, a range type over <code class="type">timestamp</code> could be
defined to have a step size of an hour, in which case the canonicalization
function would need to round off bounds that weren't a multiple of an hour,
or perhaps throw an error instead.
</p><p>
In addition, any range type that is meant to be used with GiST or SP-GiST
indexes should define a subtype difference, or <code class="literal">subtype_diff</code>,
function. (The index will still work without <code class="literal">subtype_diff</code>,
but it is likely to be considerably less efficient than if a difference
function is provided.) The subtype difference function takes two input
values of the subtype, and returns their difference
(i.e., <em class="replaceable"><code>X</code></em> minus <em class="replaceable"><code>Y</code></em>) represented as
a <code class="type">float8</code> value. In our example above, the
function <code class="function">float8mi</code> that underlies the regular <code class="type">float8</code>
minus operator can be used; but for any other subtype, some type
conversion would be necessary. Some creative thought about how to
represent differences as numbers might be needed, too. To the greatest
extent possible, the <code class="literal">subtype_diff</code> function should agree with
the sort ordering implied by the selected operator class and collation;
that is, its result should be positive whenever its first argument is
greater than its second according to the sort ordering.
</p><p>
A less-oversimplified example of a <code class="literal">subtype_diff</code> function is:
</p><pre class="programlisting">
CREATE FUNCTION time_subtype_diff(x time, y time) RETURNS float8 AS
'SELECT EXTRACT(EPOCH FROM (x - y))' LANGUAGE sql STRICT IMMUTABLE;
CREATE TYPE timerange AS RANGE (
subtype = time,
subtype_diff = time_subtype_diff
);
SELECT '[11:10, 23:00]'::timerange;
</pre><p>
See <a class="xref" href="sql-createtype.html" title="CREATE TYPE"><span class="refentrytitle">CREATE TYPE</span></a> for more information about creating
range types.
</p></div><div class="sect2" id="RANGETYPES-INDEXING"><div class="titlepage"><div><div><h3 class="title">8.17.9. Indexing</h3></div></div></div><a id="id-1.5.7.25.13.2" class="indexterm"></a><p>
GiST and SP-GiST indexes can be created for table columns of range types.
For instance, to create a GiST index:
</p><pre class="programlisting">
CREATE INDEX reservation_idx ON reservation USING GIST (during);
</pre><p>
A GiST or SP-GiST index can accelerate queries involving these range operators:
<code class="literal">=</code>,
<code class="literal">&&</code>,
<code class="literal"><@</code>,
<code class="literal">@></code>,
<code class="literal"><<</code>,
<code class="literal">>></code>,
<code class="literal">-|-</code>,
<code class="literal">&<</code>, and
<code class="literal">&></code>
(see <a class="xref" href="functions-range.html#RANGE-OPERATORS-TABLE" title="Table 9.50. Range Operators">Table 9.50</a> for more information).
</p><p>
In addition, B-tree and hash indexes can be created for table columns of
range types. For these index types, basically the only useful range
operation is equality. There is a B-tree sort ordering defined for range
values, with corresponding <code class="literal"><</code> and <code class="literal">></code> operators,
but the ordering is rather arbitrary and not usually useful in the real
world. Range types' B-tree and hash support is primarily meant to
allow sorting and hashing internally in queries, rather than creation of
actual indexes.
</p></div><div class="sect2" id="RANGETYPES-CONSTRAINT"><div class="titlepage"><div><div><h3 class="title">8.17.10. Constraints on Ranges</h3></div></div></div><a id="id-1.5.7.25.14.2" class="indexterm"></a><p>
While <code class="literal">UNIQUE</code> is a natural constraint for scalar
values, it is usually unsuitable for range types. Instead, an
exclusion constraint is often more appropriate
(see <a class="link" href="sql-createtable.html#SQL-CREATETABLE-EXCLUDE">CREATE TABLE
... CONSTRAINT ... EXCLUDE</a>). Exclusion constraints allow the
specification of constraints such as <span class="quote">“<span class="quote">non-overlapping</span>”</span> on a
range type. For example:
</p><pre class="programlisting">
CREATE TABLE reservation (
during tsrange,
EXCLUDE USING GIST (during WITH &&)
);
</pre><p>
That constraint will prevent any overlapping values from existing
in the table at the same time:
</p><pre class="programlisting">
INSERT INTO reservation VALUES
('[2010-01-01 11:30, 2010-01-01 15:00)');
INSERT 0 1
INSERT INTO reservation VALUES
('[2010-01-01 14:45, 2010-01-01 15:45)');
ERROR: conflicting key value violates exclusion constraint "reservation_during_excl"
DETAIL: Key (during)=(["2010-01-01 14:45:00","2010-01-01 15:45:00")) conflicts
with existing key (during)=(["2010-01-01 11:30:00","2010-01-01 15:00:00")).
</pre><p>
</p><p>
You can use the <a class="link" href="btree-gist.html" title="F.7. btree_gist"><code class="literal">btree_gist</code></a>
extension to define exclusion constraints on plain scalar data types, which
can then be combined with range exclusions for maximum flexibility. For
example, after <code class="literal">btree_gist</code> is installed, the following
constraint will reject overlapping ranges only if the meeting room numbers
are equal:
</p><pre class="programlisting">
CREATE EXTENSION btree_gist;
CREATE TABLE room_reservation (
room text,
during tsrange,
EXCLUDE USING GIST (room WITH =, during WITH &&)
);
INSERT INTO room_reservation VALUES
('123A', '[2010-01-01 14:00, 2010-01-01 15:00)');
INSERT 0 1
INSERT INTO room_reservation VALUES
('123A', '[2010-01-01 14:30, 2010-01-01 15:30)');
ERROR: conflicting key value violates exclusion constraint "room_reservation_room_during_excl"
DETAIL: Key (room, during)=(123A, ["2010-01-01 14:30:00","2010-01-01 15:30:00")) conflicts
with existing key (room, during)=(123A, ["2010-01-01 14:00:00","2010-01-01 15:00:00")).
INSERT INTO room_reservation VALUES
('123B', '[2010-01-01 14:30, 2010-01-01 15:30)');
INSERT 0 1
</pre><p>
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