diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ltree.sgml | 38 |
1 files changed, 24 insertions, 14 deletions
diff --git a/doc/src/sgml/ltree.sgml b/doc/src/sgml/ltree.sgml index ae4b33ec85e..d7dd55540a8 100644 --- a/doc/src/sgml/ltree.sgml +++ b/doc/src/sgml/ltree.sgml @@ -60,7 +60,8 @@ <type>lquery</type> represents a regular-expression-like pattern for matching <type>ltree</type> values. A simple word matches that label within a path. A star symbol (<literal>*</literal>) matches zero - or more labels. For example: + or more labels. These can be joined with dots to form a pattern that + must match the whole label path. For example: <synopsis> foo <lineannotation>Match the exact label path <literal>foo</literal></lineannotation> *.foo.* <lineannotation>Match any label path containing the label <literal>foo</literal></lineannotation> @@ -69,19 +70,25 @@ foo <lineannotation>Match the exact label path <literal>foo</literal></l </para> <para> - Star symbols can also be quantified to restrict how many labels - they can match: + Both star symbols and simple words can be quantified to restrict how many + labels they can match: <synopsis> *{<replaceable>n</replaceable>} <lineannotation>Match exactly <replaceable>n</replaceable> labels</lineannotation> *{<replaceable>n</replaceable>,} <lineannotation>Match at least <replaceable>n</replaceable> labels</lineannotation> *{<replaceable>n</replaceable>,<replaceable>m</replaceable>} <lineannotation>Match at least <replaceable>n</replaceable> but not more than <replaceable>m</replaceable> labels</lineannotation> -*{,<replaceable>m</replaceable>} <lineannotation>Match at most <replaceable>m</replaceable> labels — same as </lineannotation> *{0,<replaceable>m</replaceable>} +*{,<replaceable>m</replaceable>} <lineannotation>Match at most <replaceable>m</replaceable> labels — same as </lineannotation>*{0,<replaceable>m</replaceable>} +foo{<replaceable>n</replaceable>,<replaceable>m</replaceable>} <lineannotation>Match at least <replaceable>n</replaceable> but not more than <replaceable>m</replaceable> occurrences of <literal>foo</literal></lineannotation> +foo{,} <lineannotation>Match any number of occurrences of <literal>foo</literal>, including zero</lineannotation> </synopsis> + In the absence of any explicit quantifier, the default for a star symbol + is to match any number of labels (that is, <literal>{,}</literal>) while + the default for a non-star item is to match exactly once (that + is, <literal>{1}</literal>). </para> <para> There are several modifiers that can be put at the end of a non-star - label in <type>lquery</type> to make it match more than just the exact match: + <type>lquery</type> item to make it match more than just the exact match: <synopsis> @ <lineannotation>Match case-insensitively, for example <literal>a@</literal> matches <literal>A</literal></lineannotation> * <lineannotation>Match any label with this prefix, for example <literal>foo*</literal> matches <literal>foobar</literal></lineannotation> @@ -97,17 +104,20 @@ foo <lineannotation>Match the exact label path <literal>foo</literal></l </para> <para> - Also, you can write several possibly-modified labels separated with - <literal>|</literal> (OR) to match any of those labels, and you can put - <literal>!</literal> (NOT) at the start to match any label that doesn't - match any of the alternatives. + Also, you can write several possibly-modified non-star items separated with + <literal>|</literal> (OR) to match any of those items, and you can put + <literal>!</literal> (NOT) at the start of a non-star group to match any + label that doesn't match any of the alternatives. A quantifier, if any, + goes at the end of the group; it means some number of matches for the + group as a whole (that is, some number of labels matching or not matching + any of the alternatives). </para> <para> Here's an annotated example of <type>lquery</type>: <programlisting> -Top.*{0,2}.sport*@.!football|tennis.Russ*|Spain -a. b. c. d. e. +Top.*{0,2}.sport*@.!football|tennis{1,}.Russ*|Spain +a. b. c. d. e. </programlisting> This query will match any label path that: </para> @@ -129,8 +139,8 @@ a. b. c. d. e. </listitem> <listitem> <para> - then a label not matching <literal>football</literal> nor - <literal>tennis</literal> + then has one or more labels, none of which + match <literal>football</literal> nor <literal>tennis</literal> </para> </listitem> <listitem> @@ -632,7 +642,7 @@ ltreetest=> SELECT path FROM test WHERE path ~ '*.Astronomy.*'; Top.Collections.Pictures.Astronomy.Astronauts (7 rows) -ltreetest=> SELECT path FROM test WHERE path ~ '*.!pictures@.*.Astronomy.*'; +ltreetest=> SELECT path FROM test WHERE path ~ '*.!pictures@.Astronomy.*'; path ------------------------------------ Top.Science.Astronomy |