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Mention fallback case for type coercion in description

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of function resolution procedure.
This commit is contained in:
Tom Lane 2000-12-19 00:54:59 +00:00
parent e4eb91048c
commit e34d442dbb
1 changed files with 16 additions and 6 deletions
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22
doc/src/sgml/typeconv.sgml
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@ -279,7 +279,7 @@ select "string"
category if any candidate accepts that category (this bias towards string category if any candidate accepts that category (this bias towards string
is appropriate since an unknown-type literal does look like a string). is appropriate since an unknown-type literal does look like a string).
Otherwise, if all the remaining candidates accept the same type category, Otherwise, if all the remaining candidates accept the same type category,
select that category; otherwise raise an error because select that category; otherwise fail because
the correct choice cannot be deduced without more clues. Also note whether the correct choice cannot be deduced without more clues. Also note whether
any of the candidates accept a preferred datatype within the selected category. any of the candidates accept a preferred datatype within the selected category.
Now discard operator candidates that do not accept the selected type category; Now discard operator candidates that do not accept the selected type category;
@ -292,7 +292,7 @@ argument.
<para> <para>
If only one candidate remains, use it. If no candidate or more than one If only one candidate remains, use it. If no candidate or more than one
candidate remains, candidate remains,
then raise an error. then fail.
</para> </para>
</step> </step>
</substeps> </substeps>
@ -488,7 +488,7 @@ select "string"
category if any candidate accepts that category (this bias towards string category if any candidate accepts that category (this bias towards string
is appropriate since an unknown-type literal does look like a string). is appropriate since an unknown-type literal does look like a string).
Otherwise, if all the remaining candidates accept the same type category, Otherwise, if all the remaining candidates accept the same type category,
select that category; otherwise raise an error because select that category; otherwise fail because
the correct choice cannot be deduced without more clues. Also note whether the correct choice cannot be deduced without more clues. Also note whether
any of the candidates accept a preferred datatype within the selected category. any of the candidates accept a preferred datatype within the selected category.
Now discard operator candidates that do not accept the selected type category; Now discard operator candidates that do not accept the selected type category;
@ -501,11 +501,22 @@ argument.
<para> <para>
If only one candidate remains, use it. If no candidate or more than one If only one candidate remains, use it. If no candidate or more than one
candidate remains, candidate remains,
then raise an error. then fail.
</para> </para>
</step> </step>
</substeps> </substeps>
</step> </step>
<step performance="required">
<para>
If no best match could be identified, see whether the function call appears
to be a trivial type coercion request. This happens if the function call
has just one argument and the function name is the same as the (internal)
name of some datatype. Furthermore, the function argument must be either
an unknown-type literal or a type that is binary-compatible with the named
datatype. When these conditions are met, the function argument is coerced
to the named datatype.
</para>
</step>
</procedure> </procedure>
<sect2> <sect2>
@ -699,8 +710,7 @@ Otherwise, ignore the <type>unknown</type> inputs while choosing the type.
<step performance="required"> <step performance="required">
<para> <para>
If the non-unknown inputs are not all of the same type category, raise an If the non-unknown inputs are not all of the same type category, fail.
error.
</para></step> </para></step>
<step performance="required"> <step performance="required">