The new per-dictionary settings control regex match semantics around
case sensitivity and the '.' wildcard with newlines. They must be set at
the dictionary level since they're applied to regex engines at
pattern-compile-time.
- regexp_dict_flag_case_insensitive: case insensitive matching
- regexp_dict_flag_dotall: '.' matches all characters including newlines
They correspond to HS_FLAG_CASELESS and HS_FLAG_DOTALL in Vectorscan
and case_sensitive and dot_nl in RE2. These are the most useful options
compatible with the internal behavior of RegExpTreeDictionary around
splitting up simple and complex patterns between Vectorscan and RE2.
The alternative is to use (?i) and/or (?s) for all patterns. However,
(?s) isn't handled properly by OptimizedRegularExpression::analyze().
And while (?i) is, it still causes the dictionary to treat the pattern
as "complex" for sequential scanning with RE2 rather than multi-matching
with Vectorscan, even though Vectorscan supports case insensitive
literal matching. Setting dictionary-wide flags is both more convenient,
and circumvents these problems.
This reverts the following commits:
- e77dd81036
- e8527e720b
Additionally, functional tests are added.
When scanning complex regexp nodes sequentially with RE2, the old code
has an optimization to break out of the loop early upon finding a leaf
node that matches. This is an invalid optimization because there's no
guarantee that it's actually a VALID match, because its parents might
NOT have matched. Semantically, a user would expect this match to be
discarded and for the search to continue. Instead, since we skipped
matching after the first false positive, subsequent nodes that would
have matched are missing from the output value. This affects both
dictGet and dictGetAll.
It's difficult to distinguish a true positive from a false positive
while looping through complex_regexp_nodes because we would have to scan
all the parents of a matching node to confirm a true positive. Trying to
do this might actually end up being slower than just scanning every
complex regexp node, because complex_regexp_nodes is only a subset of
all the tree nodes; we may end up duplicating work with scanning
that Vectorscan has already done, depending on whether the parent nodes
are "simple" or "complex". So instead of trying to fix this
optimization, just remove it entirely.
This function outputs an array of attribute values from all regexp nodes
that matched in a regexp tree dictionary. An optional final argument can
be passed to limit the array size.
