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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2023-07-19 11:00:34 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2023-07-19 11:00:34 -0400 |
| commit | 22d0c30bd9662e48fb0d27253fec6a43c7673f13 (patch) | |
| tree | 66c3b1d657b0023d69483e521b17c631778a03cd | |
| parent | 04911fa767fda444c1a883a6ece32a0674cffd03 (diff) | |
| download | postgresql-22d0c30bd9662e48fb0d27253fec6a43c7673f13.tar.gz postgresql-22d0c30bd9662e48fb0d27253fec6a43c7673f13.zip | |
Doc: improve description of IN and row-constructor comparisons.
IN and NOT IN work fine on records and arrays, so just say that
they accept "expressions" not "scalar expressions". I think that
that phrasing was meant to say that they don't work on set-returning
expressions, but that's not the common meaning of "scalar".
Revise the description of row-constructor comparisons to make it
perhaps a bit less confusing. (This partially reverts some
dubious wording changes made by commit f56651519.)
Per gripe from Ilya Nenashev. Back-patch to supported branches.
In HEAD and v16, also drop a NOTE about pre-8.2 behavior, which
is hopefully no longer of interest to anybody.
Discussion: https://postgr.es/m/168968062460.632.14303906825812821399@wrigleys.postgresql.org
| -rw-r--r-- | doc/src/sgml/func.sgml | 30 |
1 files changed, 14 insertions, 16 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 827c4afc654..2ea31830cbb 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -16858,7 +16858,7 @@ WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2); <para> The right-hand side is a parenthesized list - of scalar expressions. The result is <quote>true</quote> if the left-hand expression's + of expressions. The result is <quote>true</quote> if the left-hand expression's result is equal to any of the right-hand expressions. This is a shorthand notation for @@ -16889,7 +16889,7 @@ OR <para> The right-hand side is a parenthesized list - of scalar expressions. The result is <quote>true</quote> if the left-hand expression's + of expressions. The result is <quote>true</quote> if the left-hand expression's result is unequal to all of the right-hand expressions. This is a shorthand notation for @@ -17000,26 +17000,24 @@ AND <para> Each side is a row constructor, as described in <xref linkend="sql-syntax-row-constructors"/>. - The two row values must have the same number of fields. - Each side is evaluated and they are compared row-wise. Row constructor - comparisons are allowed when the <replaceable>operator</replaceable> is + The two row constructors must have the same number of fields. + The given <replaceable>operator</replaceable> is applied to each pair + of corresponding fields. (Since the fields could be of different + types, this means that a different specific operator could be selected + for each pair.) + All the selected operators must be members of some B-tree operator + class, or be the negator of an <literal>=</literal> member of a B-tree + operator class, meaning that row constructor comparison is only + possible when the <replaceable>operator</replaceable> is <literal>=</literal>, <literal><></literal>, <literal><</literal>, <literal><=</literal>, - <literal>></literal> or - <literal>>=</literal>. - Every row element must be of a type which has a default B-tree operator - class or the attempted comparison may generate an error. + <literal>></literal>, or + <literal>>=</literal>, + or has semantics similar to one of these. </para> - <note> - <para> - Errors related to the number or types of elements might not occur if - the comparison is resolved using earlier columns. - </para> - </note> - <para> The <literal>=</literal> and <literal><></literal> cases work slightly differently from the others. Two rows are considered |