This provides a handy way to get, say, the last field of the string.
Use of a negative index in this way has precedent in the nearby
left() and right() functions.
The implementation scans the string twice when N < -1, but it seems
likely that N = -1 will be the huge majority of actual use cases,
so I'm not really excited about adding complexity to avoid that.
Nikhil Benesch, reviewed by Jacob Champion; cosmetic tweakage by me
Discussion: https://postgr.es/m/cbb7f861-6162-3a51-9823-97bc3aa0b638@gmail.com
SQL:1999 had syntax
SUBSTRING(text FROM pattern FOR escapechar)
but this was replaced in SQL:2003 by the more clear
SUBSTRING(text SIMILAR pattern ESCAPE escapechar)
but this was never implemented in PostgreSQL. This patch adds that
new syntax as an alternative in the parser, and updates documentation
and tests to indicate that this is the preferred alternative now.
Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>
Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Reviewed-by: Fabien COELHO <coelho@cri.ensmp.fr>
Discussion: https://www.postgresql.org/message-id/flat/a15db31c-d0f8-8ce0-9039-578a31758adb%402ndquadrant.com
Since the existing bit number argument can't exceed INT32_MAX, it's
not possible for these functions to manipulate bits beyond the first
256MB of a bytea value. Lift that restriction by redeclaring the
bit number arguments as int8 (which requires a catversion bump,
hence is not back-patchable).
The similarly-named functions for bit/varbit don't really have a
problem because we restrict those types to at most VARBITMAXLEN bits;
hence leave them alone.
While here, extend the encode/decode functions in utils/adt/encode.c
to allow dealing with values wider than 1GB. This is not a live bug
or restriction in current usage, because no input could be more than
1GB, and since none of the encoders can expand a string more than 4X,
the result size couldn't overflow uint32. But it might be desirable
to support more in future, so make the input length values size_t
and the potential-output-length values uint64.
Also add some test cases to improve the miserable code coverage
of these functions.
Movead Li, editorialized some by me; also reviewed by Ashutosh Bapat
Discussion: https://postgr.es/m/20200312115135445367128@highgo.ca
SQL includes provisions for numeric Unicode escapes in string
literals and identifiers. Previously we only accepted those
if they represented ASCII characters or the server encoding
was UTF-8, making the conversion to internal form trivial.
This patch adjusts things so that we'll call the appropriate
encoding conversion function in less-trivial cases, allowing
the escape sequence to be accepted so long as it corresponds
to some character available in the server encoding.
This also applies to processing of Unicode escapes in JSONB.
However, the old restriction still applies to client-side
JSON processing, since that hasn't got access to the server's
encoding conversion infrastructure.
This patch includes some lexer infrastructure that simplifies
throwing errors with error cursors pointing into the middle of
a string (or other complex token). For the moment I only used
it for errors relating to Unicode escapes, but we might later
expand the usage to some other cases.
Patch by me, reviewed by John Naylor.
Discussion: https://postgr.es/m/2393.1578958316@sss.pgh.pa.us
Previously, the core scanner's yy_transition[] array had 37045 elements.
Since that number is larger than INT16_MAX, Flex generated the array to
contain 32-bit integers. By reimplementing some of the bulkier scanner
rules, this patch reduces the array to 20495 elements. The much smaller
total length, combined with the consequent use of 16-bit integers for
the array elements reduces the binary size by over 200kB. This was
accomplished in two ways:
1. Consolidate handling of quote continuations into a new start condition,
rather than duplicating that logic for five different string types.
2. Treat Unicode strings and identifiers followed by a UESCAPE sequence
as three separate tokens, rather than one. The logic to de-escape
Unicode strings is moved to the filter code in parser.c, which already
had the ability to provide special processing for token sequences.
While we could have implemented the conversion in the grammar, that
approach was rejected for performance and maintainability reasons.
Performance in microbenchmarks of raw parsing seems equal or slightly
faster in most cases, and it's reasonable to expect that in real-world
usage (with more competition for the CPU cache) there will be a larger
win. The exception is UESCAPE sequences; lexing those is about 10%
slower, primarily because the scanner now has to be called three times
rather than one. This seems acceptable since that feature is very
rarely used.
The psql and epcg lexers are likewise modified, primarily because we
want to keep them all in sync. Since those lexers don't use the
space-hogging -CF option, the space savings is much less, but it's
still good for perhaps 10kB apiece.
While at it, merge the ecpg lexer's handling of C-style comments used
in SQL and in C. Those have different rules regarding nested comments,
but since we already have the ability to keep track of the previous
start condition, we can use that to handle both cases within a single
start condition. This matches the core scanner more closely.
John Naylor
Discussion: https://postgr.es/m/CACPNZCvaoa3EgVWm5yZhcSTX6RAtaLgniCPcBVOCwm8h3xpWkw@mail.gmail.com
Commit 9556aa01c rearranged the innards of text_position() in a way
that would make it not work for empty search strings. Which is fine,
because all callers of that code special-case an empty pattern in
some way. However, the primary use-case (text_position itself) got
special-cased incorrectly: historically it's returned 1 not 0 for
an empty search string. Restore the historical behavior.
Per complaint from Austin Drenski (via Shay Rojansky).
Back-patch to v12 where it got broken.
Discussion: https://postgr.es/m/CADT4RqAz7oN4vkPir86Kg1_mQBmBxCp-L_=9vRpgSNPJf0KRkw@mail.gmail.com
As a result of some long-ago quick hacks, the SIMILAR TO operator
and the corresponding flavor of substring() interpreted "ESCAPE NULL"
as selecting the default escape character '\'. This is both
surprising and not per spec: the standard is clear that these
functions should return NULL for NULL input.
Additionally, because of inconsistency of the strictness markings
of 3-argument substring() and similar_escape(), the planner could not
inline the SQL definition of substring(), resulting in a substantial
performance penalty compared to the underlying POSIX substring()
function.
The simplest fix for this would be to change the strictness marking
of similar_escape(), but if we do that we risk breaking existing views
that depend on that function. Hence, leave similar_escape() as-is
as a compatibility function, and instead invent a new function
similar_to_escape() that comes in two strict variants.
There are a couple of other behaviors in this area that are also
not per spec, but they are documented and seem generally at least
as sane as the spec's definition, so leave them alone. But improve
the documentation to describe them fully.
Patch by me; thanks to Álvaro Herrera and Andrew Gierth for review
and discussion.
Discussion: https://postgr.es/m/14047.1557708214@sss.pgh.pa.us
SQL's regular-expression substring() function is defined to have a
pattern argument that's separated into three subpatterns by escape-
double-quote markers; the function result is the part of the input
matching the second subpattern. The standard makes it clear that
if there is ambiguity about how to match the input to the subpatterns,
the first and third subpatterns should be taken to match the smallest
possible amount of text (i.e., they're "non greedy", in the terms of
our regex code). We were not doing it that way: the first subpattern
would eat the largest possible amount of text, causing the function
result to be shorter than what the spec requires.
Fix that by attaching explicit greediness quantifiers to the
subpatterns. (This depends on the regex fix in commit 8a29ed053;
before that, this didn't reliably change the regex engine's behavior.)
Also, by adding parentheses around each subpattern, we ensure that
"|" (OR) in the subpatterns behave sanely. Previously, "|" in the
first or third subpatterns didn't work.
This patch also makes the function throw error if you write more than
two escape-double-quote markers, and do something sane if you write
just one, and document that behavior. Previously, an odd number of
markers led to a confusing complaint about unbalanced parentheses,
while extra pairs of markers were just ignored. (Note that the spec
requires exactly two markers, but we've historically allowed there
to be none, and this patch preserves the old behavior for that case.)
In passing, adjust some substring() test cases that didn't really
prove what they said they were testing for: they used patterns
that didn't match the data string, so that the output would be
NULL whether or not the function was really strict.
Although this is certainly a bug fix, changing the behavior in back
branches seems undesirable: applications could perhaps be depending on
the old behavior, since it's not obviously wrong unless you read the
spec very closely. Hence, no back-patch.
Discussion: https://postgr.es/m/5bb27a41-350d-37bf-901e-9d26f5592dd0@charter.net
c251336 has added some tests to check if a toast relation should be
empty or not, hardcoding the toast relation name when calling
pg_relation_size(). pg_class.reltoastrelid offers the same information,
so simplify the tests to use that.
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20190403065949.GH3298@paquier.xyz
Commit c8ea87e4b introduced a temporary conversion buffer for
substrings extracted during regexp splits. Unfortunately the code that
sized it was failing to ignore the effects of ignored degenerate
regexp matches, so for regexp_split_* calls it could under-size the
buffer in such cases.
Fix, and add some regression test cases (though those will only catch
the bug if run in a multibyte encoding).
Backpatch to 9.3 as the faulty code was.
Thanks to the PostGIS project, Regina Obe and Paul Ramsey for the
report (via IRC) and assistance in analysis. Patch by me.
Add the user-callable functions sha224, sha256, sha384, sha512. We
already had these in the C code to support SCRAM, but there was no test
coverage outside of the SCRAM tests. Adding these as user-callable
functions allows writing some tests. Also, we have a user-callable md5
function but no more modern alternative, which led to wide use of md5 as
a general-purpose hash function, which leads to occasional complaints
about using md5.
Also mark the existing md5 functions as leak-proof.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
We'd find the same match twice if it was of zero length and not immediately
adjacent to the previous match. replace_text_regexp() got similar cases
right, so adjust this search logic to match that. Note that even though
the regexp_split_to_xxx() functions share this code, they did not display
equivalent misbehavior, because the second match would be considered
degenerate and ignored.
Jeevan Chalke, with some cosmetic changes by me.
In most cases, these were just references to the SQL standard in
general. In a few cases, a contrast was made between SQL92 and later
standards -- those have been kept unchanged.
for sure ;-)). It now also optimizes more cases, such as %_%_. Improve
comments too. Per bug #5478.
In passing, also rename the TCHAR macro to GETCHAR, because pgindent is
messing with the formatting of the former (apparently it now thinks TCHAR
is a typedef name).
Back-patch to 8.3, where the bug was introduced.
and implement OVERLAY() for bit strings and bytea.
In passing also convert text OVERLAY() to a true built-in, instead of
relying on a SQL function.
Leonardo F, reviewed by Kevin Grittner
Both hex format and the traditional "escape" format are automatically
handled on input. The output format is selected by the new GUC variable
bytea_output.
As committed, bytea_output defaults to HEX, which is an *incompatible
change*. We will keep it this way for awhile for testing purposes, but
should consider whether to switch to the more backwards-compatible
default of ESCAPE before 8.5 is released.
Peter Eisentraut
this case is worth a special code path, but a special code path that gets
the boundary condition wrong is definitely no good. Per bug #4821 from
Andrew Gierth.
In passing, clean up some minor code formatting issues (excess parentheses
and blank lines in odd places).
Back-patch to 8.3, where the bug was introduced.
that cached compiled patterns will still be there when the function is next
called. Clean up looping logic, thereby fixing bug identified by Pavel
Stehule. Share setup code between the two functions, add some comments, and
avoid risky mixing of int and size_t variables. Clean up the documentation a
tad, and accept all the flag characters mentioned in table 9-19 rather than
just a subset.
from the other string-category types; this eliminates a lot of surprising
interpretations that the parser could formerly make when there was no directly
applicable operator.
Create a general mechanism that supports casts to and from the standard string
types (text,varchar,bpchar) for *every* datatype, by invoking the datatype's
I/O functions. These new casts are assignment-only in the to-string direction,
explicit-only in the other, and therefore should create no surprising behavior.
Remove a bunch of thereby-obsoleted datatype-specific casting functions.
The "general mechanism" is a new expression node type CoerceViaIO that can
actually convert between *any* two datatypes if their external text
representations are compatible. This is more general than needed for the
immediate feature, but might be useful in plpgsql or other places in future.
This commit does nothing about the issue that applying the concatenation
operator || to non-text types will now fail, often with strange error messages
due to misinterpreting the operator as array concatenation. Since it often
(not always) worked before, we should either make it succeed or at least give
a more user-friendly error; but details are still under debate.
Peter Eisentraut and Tom Lane
This commit breaks any code that assumes that the mere act of forming a tuple
(without writing it to disk) does not "toast" any fields. While all available
regression tests pass, I'm not totally sure that we've fixed every nook and
cranny, especially in contrib.
Greg Stark with some help from Tom Lane
and regexp_split_to_table. These functions provide access to the
capture groups resulting from a POSIX regular expression match,
and provide the ability to split a string on a POSIX regular
expression, respectively. Patch from Jeremy Drake; code review by
Neil Conway, additional comments and suggestions from Tom and
Peter E.
This patch bumps the catversion, adds some regression tests,
and updates the docs.
The specification of this function is as follows.
regexp_replace(source text, pattern text, replacement text, [flags
text])
returns text
Replace string that matches to regular expression in source text to
replacement text.
- pattern is regular expression pattern.
- replacement is replace string that can use '\1'-'\9', and '\&'.
'\1'-'\9': back reference to the n'th subexpression.
'\&' : entire matched string.
- flags can use the following values:
g: global (replace all)
i: ignore case
When the flags is not specified, case sensitive, replace the first
instance only.
Atsushi Ogawa
from Abhijit Menon-Sen, minor editorialization from Neil Conway. Also,
improve md5(text) to allocate a constant-sized buffer on the stack
rather than via palloc.
Catalog version bumped.
blanks, in hopes of reducing the surprise factor for newbies. Remove
redundant operators for VARCHAR (it depends wholly on TEXT operations now).
Clean up resolution of ambiguous operators/functions to avoid surprising
choices for domains: domains are treated as equivalent to their base types
and binary-coercibility is no longer considered a preference item when
choosing among multiple operators/functions. IsBinaryCoercible now correctly
reflects the notion that you need *only* relabel the type to get from type
A to type B: that is, a domain is binary-coercible to its base type, but
not vice versa. Various marginal cleanup, including merging the essentially
duplicate resolution code in parse_func.c and parse_oper.c. Improve opr_sanity
regression test to understand about binary compatibility (using pg_cast),
and fix a couple of small errors in the catalogs revealed thereby.
Restructure "special operator" handling to fetch operators via index opclasses
rather than hardwiring assumptions about names (cleans up the pattern_ops
stuff a little).
documentation and regression test mods. It seemed small and unobtrusive enough
to not require a specific proposal on the hackers list -- but if not, let me
know and I'll make a pitch. Otherwise, if there are no objections please apply.
Joe Conway
the SQL99 standard. (I'm not sure that the character-class features are
quite right, but that can be fixed later.) Document SQL99 and POSIX
regexps as being different features; provide variants of SUBSTRING for
each.
to be flexible about assignment casts without introducing ambiguity in
operator/function resolution. Introduce a well-defined promotion hierarchy
for numeric datatypes (int2->int4->int8->numeric->float4->float8).
Change make_const to initially label numeric literals as int4, int8, or
numeric (never float8 anymore).
Explicitly mark Func and RelabelType nodes to indicate whether they came
from a function call, explicit cast, or implicit cast; use this to do
reverse-listing more accurately and without so many heuristics.
Explicit casts to char, varchar, bit, varbit will truncate or pad without
raising an error (the pre-7.2 behavior), while assigning to a column without
any explicit cast will still raise an error for wrong-length data like 7.3.
This more nearly follows the SQL spec than 7.2 behavior (we should be
reporting a 'completion condition' in the explicit-cast cases, but we have
no mechanism for that, so just do silent truncation).
Fix some problems with enforcement of typmod for array elements;
it didn't work at all in 'UPDATE ... SET array[n] = foo', for example.
Provide a generalized array_length_coerce() function to replace the
specialized per-array-type functions that used to be needed (and were
missing for NUMERIC as well as all the datetime types).
Add missing conversions int8<->float4, text<->numeric, oid<->int8.
initdb forced.
> Hannu Krosing wrote:
>
>> It seems that my last mail on this did not get through to the list
>> ;(
>>
>> Please consider renaming the new builtin function
>> split(text,text,int)
>>
>> to something else, perhaps
>>
>> split_part(text,text,int)
>>
>> (like date_part)
>>
>> The reason for this request is that 3 most popular scripting
>> languages (perl, python, php) all have also a function with similar
>> signature, but returning an array instead of single element and the
>> (optional) third argument is limit (maximum number of splits to
>> perform)
>>
>> I think that it would be good to have similar function in (some
>> future release of) postgres, but if we now let in a function with
>> same name and arguments but returning a single string instead an
>> array of them, then we will need to invent a new and not so easy to
>> recognise name for the "real" split function.
>>
>
> This is a good point, and I'm not opposed to changing the name, but
> it is too bad your original email didn't get through before beta1 was
> rolled. The change would now require an initdb, which I know we were
> trying to avoid once beta started (although we could change it
> without *requiring* an initdb I suppose).
>
> I guess if we do end up needing an initdb for other reasons, we
> should make this change too. Any other opinions? Is split_part an
> acceptable name?
>
> Also, if we add a todo to produce a "real" split function that
> returns an array, similar to those languages, I'll take it for 7.4.
No one commented on the choice of name, so the attached patch changes
the name of split(text,text,int) to split_part(text,text,int) per
Hannu's recommendation above. This can be applied without an initdb if
current beta testers are advised to run:
update pg_proc set proname = 'split_part' where proname = 'split';
in the case they want to use this function. Regression and doc fix is
also included in the patch.
Joe Conway
CVS HEAD):
Amended "strings" regression test. TOAST tests now insert two values
with storage set to "external", to exercise properly the TOAST slice
routines which fetch only a subset of the chunks.
Changed now-misleading comment on AlterTableCreateToastTable in
tablecmds.c, because both columns of the index on a toast table are now
used.
John Gray
replace(string, from, to)
-- replaces all occurrences of "from" in "string" to "to"
split(string, fldsep, column)
-- splits "string" on "fldsep" and returns "column" number piece
to_hex(int32_num) & to_hex(int64_num)
-- takes integer number and returns as hex string
Joe Conway
Implement SQL99 SIMILAR TO as a synonym for our existing operator "~".
Implement SQL99 regular expression SUBSTRING(string FROM pat FOR escape).
Extend the definition to make the FOR clause optional.
Define textregexsubstr() to actually implement this feature.
Update the regression test to include these new string features.
All tests pass.
Rename the regular expression support routines from "pg95_xxx" to "pg_xxx".
Define CREATE CHARACTER SET in the parser per SQL99. No implementation yet.
right, but it failed to get the padding case right.
This was obscured by subsequent application of bpchar() in all but one
regression test case, and that one didn't fail in an obvious way ---
trailing blanks are hard to see. Add another test case to make it
more obvious if it breaks again.
rather than the "~~" operator; this made it easy to add ESCAPE features.
Implement ILIKE, NOT ILIKE, and the ESCAPE clause for them.
afaict this is not MultiByte clean, but lots of other stuff isn't either.
Fix up underlying support code for LIKE/NOT LIKE.
Things should be faster and does not require internal string copying.
Update regression test to add explicit checks for
LIKE/NOT LIKE/ILIKE/NOT ILIKE.
Remove colon and semi-colon operators as threatened in 7.0.
Implement SQL99 COMMIT/AND NO CHAIN.
Throw elog(ERROR) on COMMIT/AND CHAIN per spec
since we don't yet support it.
Implement SQL99 CREATE/DROP SCHEMA as equivalent to CREATE DATABASE.
This is only a stopgap or demo since schemas will have another
implementation soon.
Remove a few unused production rules to get rid of warnings
which crept in on the last commit.
Fix up tabbing in some places by removing embedded spaces.
Tom Lane