diff options
Diffstat (limited to 'src/backend/regex/re_syntax.n')
| -rw-r--r-- | src/backend/regex/re_syntax.n | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/src/backend/regex/re_syntax.n b/src/backend/regex/re_syntax.n index f37bb85abdb..4621bfc25f4 100644 --- a/src/backend/regex/re_syntax.n +++ b/src/backend/regex/re_syntax.n @@ -196,10 +196,18 @@ where a substring matching \fIre\fR begins \fB(?!\fIre\fB)\fR \fInegative lookahead\fR (AREs only), matches at any point where no substring matching \fIre\fR begins +.TP +\fB(?<=\fIre\fB)\fR +\fIpositive lookbehind\fR (AREs only), matches at any point +where a substring matching \fIre\fR ends +.TP +\fB(?<!\fIre\fB)\fR +\fInegative lookbehind\fR (AREs only), matches at any point +where no substring matching \fIre\fR ends .RE .PP -The lookahead constraints may not contain back references (see later), -and all parentheses within them are considered non-capturing. +Lookahead and lookbehind constraints may not contain back references +(see later), and all parentheses within them are considered non-capturing. .PP An RE may not end with `\fB\e\fR'. @@ -856,7 +864,8 @@ Incompatibilities of note include `\fB\eb\fR', `\fB\eB\fR', the lack of special treatment for a trailing newline, the addition of complemented bracket expressions to the things affected by newline-sensitive matching, -the restrictions on parentheses and back references in lookahead constraints, +the restrictions on parentheses and back references in lookahead/lookbehind +constraints, and the longest/shortest-match (rather than first-match) matching semantics. .PP The matching rules for REs containing both normal and non-greedy quantifiers |