fix rst

velox/docs/functions/presto/regexp.rst

@@ -32,11 +32,21 @@ limited to 20 different expressions per instance and thread of execution.
         SELECT like('abc', '%b%'); -- true
         SELECT like('a_c', '%#_%', '#'); -- true
 
-    String sequence search: There are some patterns that are equivalent to simple
-    string searches. For such constant patterns without custom-escape, velox uses
-    substring searches instead of regex searches, for example:
-        like("hello velox", "%hello%velox%")
-    is equivalent to searching for the strings "hello", "velox" in sequence.
+Not all patterns require compilation of regular expressions.
+
+| patterns  | description  | fast search mothod |
+| :------------ |:----------------------------:| -------------------:|
+| kExactlyN      | Pattern containing wildcard character '_' only, such as _, __, ____. | only check string length equal to N |
+| kAtLeastN      | Pattern containing wildcard characters ('_' or '%') only with at least one '%', such as ___%, _%__.        |   only check string length >=N  |
+| kFixed | Pattern with no wildcard characters, such as 'presto', 'foo'        |   only check if input string equals pattern |
+| kRelaxedFixed |  Pattern with single wildcard chars(_) & normal chars, such as '_pr_es_to_'.       |    only check if input string equals sub-patterns, ignore wildcard chars |
+| kPrefix | Fixed pattern followed by one or more '%', such as 'hello%', 'foo%%%%'.        |   only check if the prefix of input string matches pattern |
+| kRelaxedPrefix |   kRelaxedFixed pattern followed by one or more '%', such as '_pr_es_to_%', '_pr_es_to_%%%%'.       | only check the prefix of input string matches pattern, and ignore wildcard   |
+| kSuffix | Fixed pattern preceded by one or more '%', such as '%foo', '%%%hello'.        |   only check if the suffix of input string matches pattern |
+| kRelaxedSuffix | kRelaxedFixed preceded by one or more '%', such as '%_pr_es_to_', '%%%_pr_es_to_'.      |  only check if the suffix of input string matches pattern, ignore wildcard chars |
+| kSubstring | Patterns matching '%{c0}%', such as '%foo%%', '%%%hello%'.      |  only check if the input string contains the pattern |
+| kSubstrings | Patterns matching '%{c0}%{c1}%', such as '%%foo%%bar%%', '%foo%bar%'. Note: unlike kSubstring, kSubstrings applies only to constant patterns as pattern parsing is expensive, and not supports wildcard chars(_) and chars(#), such as '%%foo_bar%pre_sto%', '%%foo#bar#pre#sto%'   |  searching sub-strings in sequence, sunch as "%pr%es%to%" is equivalent to searching for the strings "pr", "es", "to" in sequence.   |
+
 
 .. function:: regexp_extract(string, pattern) -> varchar