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Commitf391d9d

Browse files
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Convert tab-complete's long else-if chain to a switch statement.
Rename tab-complete.c to tab-complete.in.c, create the preprocessorscript gen_tabcomplete.pl, and install Makefile/meson.build rulesto create tab-complete.c from tab-complete.in.c. The preprocessorconverts match_previous_words' else-if chain into a switch andpopulates tcpatterns[] with the data needed by the driver loop.The initial HeadMatches/TailMatches/Matches test in each else-if armis now performed in a table-driven loop. Where we get a match, thecorresponding switch case is invoked to see if the match succeeds.(It might not, if there were additional conditions in the originalelse-if test.)The total number of string comparisons done is just about thesame as it was in the previous coding; however, now that wehave table-driven logic underlying the handmade rules, thereis room to improve that. For now I haven't bothered becausetab completion is still plenty fast enough for human use.If the number of rules keeps increasing, we might somedayneed to do more in that area.The immediate benefit of all this thrashing is that C compilersfrequently don't deal well with long else-if chains. On gcc 8.5.0,this reduces the compile time of tab-complete.c by about a factor offour, while MSVC is reported to crash outright with the previouscoding.Discussion:https://postgr.es/m/2208466.1720729502@sss.pgh.pa.us
1 parentbd1276a commitf391d9d

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5 files changed

+323
-3
lines changed

5 files changed

+323
-3
lines changed

‎src/bin/psql/.gitignore

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
11
/psqlscanslash.c
2+
/tab-complete.c
23
/sql_help.h
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/sql_help.c
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/psql

‎src/bin/psql/Makefile

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -62,6 +62,9 @@ psqlscanslash.c: FLEXFLAGS = -Cfe -p -p
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psqlscanslash.c: FLEX_NO_BACKUP=yes
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psqlscanslash.c: FLEX_FIX_WARNING=yes
6464

65+
tab-complete.c: gen_tabcomplete.pl tab-complete.in.c
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$(PERL)$^ --outfile$@
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6568
install: all installdirs
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$(INSTALL_PROGRAM) psql$(X)'$(DESTDIR)$(bindir)/psql$(X)'
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$(INSTALL_DATA)$(srcdir)/psqlrc.sample'$(DESTDIR)$(datadir)/psqlrc.sample'
@@ -75,7 +78,7 @@ uninstall:
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cleandistclean:
7679
rm -f psql$(X)$(OBJS) lex.backup
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rm -rf tmp_check
78-
rm -f sql_help.h sql_help.c psqlscanslash.c
81+
rm -f sql_help.h sql_help.c psqlscanslash.c tab-complete.c
7982

8083
check:
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$(prove_check)

‎src/bin/psql/gen_tabcomplete.pl

Lines changed: 306 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,306 @@
1+
#----------------------------------------------------------------------
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#
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# gen_tabcomplete.pl
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#Perl script that transforms tab-complete.in.c to tab-complete.c.
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#
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# This script converts a C else-if chain into a switch statement.
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# The else-if statements to be processed must appear at single-tab-stop
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# indentation between lines reading
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#/* BEGIN GEN_TABCOMPLETE */
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#/* END GEN_TABCOMPLETE */
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# The first clause in each if-condition must be a call of one of the
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# functions Matches, HeadMatches, TailMatches, MatchesCS, HeadMatchesCS,
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# or TailMatchesCS. Its argument(s) must be string literals or macros
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# that expand to string literals or NULL. These clauses are removed from
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# the code and replaced by "break; case N:", where N is a unique number
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# for each such case label.
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# The BEGIN GEN_TABCOMPLETE and END GEN_TABCOMPLETE lines are replaced
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# by "switch (pattern_id) {" and "}" wrapping to make a valid switch.
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# The remainder of the code is copied verbatim.
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#
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# An if-condition can also be an OR ("||") of several *Matches function
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# calls, or it can be an AND ("&&") of a *Matches call with some other
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# condition. For example,
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#
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#else if (HeadMatches("DROP", "DATABASE") && ends_with(prev_wd, '('))
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#
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# will be transformed to
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#
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#break;
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#case N:
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#if (ends_with(prev_wd, '('))
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#
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# In addition, there must be one input line that reads
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#/* Insert tab-completion pattern data here. */
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# This line is replaced in the output file by macro calls, one for each
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# replaced match condition. The output for the above example would be
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#TCPAT(N, HeadMatch, "DROP", "DATABASE"),
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# where N is the replacement case label, "HeadMatch" is the original
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# function name minus "es", and the rest are the function arguments.
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# The tab-completion data line must appear before BEGIN GEN_TABCOMPLETE.
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#
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#
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# Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
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# Portions Copyright (c) 1994, Regents of the University of California
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#
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# src/bin/psql/gen_tabcomplete.pl
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#
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#----------------------------------------------------------------------
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use strict;
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use warningsFATAL=>'all';
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use Getopt::Long;
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my$outfile ='';
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56+
GetOptions('outfile=s'=> \$outfile)ordie"$0: wrong arguments";
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openmy$infh,'<',$ARGV[0]
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ordie"$0: could not open input file '$ARGV[0]':$!\n";
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my$outfh;
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if ($outfile)
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{
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open$outfh,'>',$outfile
65+
ordie"$0: could not open output file '$outfile':$!\n";
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}
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else
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{
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$outfh = *STDOUT;
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}
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# Opening boilerplate for output file.
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printf$outfh<<EOM;
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/*-------------------------------------------------------------------------
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*
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* tab-complete.c
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* Preprocessed tab-completion code.
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*
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* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* NOTES
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* ******************************
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* *** DO NOT EDIT THIS FILE! ***
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* ******************************
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*
87+
* It has been GENERATED by src/bin/psql/gen_tabcomplete.pl
88+
*
89+
*-------------------------------------------------------------------------
90+
*/
91+
92+
#define SWITCH_CONVERSION_APPLIED
93+
94+
#line 1 "tab-complete.in.c"
95+
EOM
96+
97+
# Scan input file until we find the data-replacement label line.
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# Dump what we scan directly into the output file.
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while (<$infh>)
100+
{
101+
chomp;
102+
lastifm|^\s*/\* Insert tab-completion pattern data here\.\*/\s*$|;
103+
print$outfh"$_\n";
104+
}
105+
106+
# $table_data collects what we will substitute for the "pattern data" line.
107+
my$table_data ='';
108+
# $output_code collects code that we can't emit till after $table_data.
109+
my$output_code ='';
110+
# last case label assigned
111+
my$last_case_label = 0;
112+
113+
# We emit #line directives to keep the output file's line numbering in sync
114+
# with the line numbering of the original, to simplify compiler error message
115+
# reading and debugging.
116+
my$next_line_no =$. + 1;
117+
$output_code .="#line${next_line_no}\"tab-complete.in.c\"\n";
118+
119+
# Scan until we find the BEGIN GEN_TABCOMPLETE line.
120+
# Add the scanned code to $output_code verbatim.
121+
while (<$infh>)
122+
{
123+
chomp;
124+
lastifm|^\s*/\* BEGIN GEN_TABCOMPLETE\*/\s*$|;
125+
$output_code .=$_ ."\n";
126+
}
127+
128+
# Emit the switch-starting lines.
129+
$output_code .="\tswitch (pattern_id)\n";
130+
$output_code .="\t{\n";
131+
132+
# Keep line numbering in sync.
133+
$next_line_no =$. + 1;
134+
$output_code .="#line${next_line_no}\"tab-complete.in.c\"\n";
135+
136+
# Scan input file, collecting outer-level else-if conditions
137+
# to pass to process_else_if.
138+
# Lines that aren't else-if conditions go to $output_code verbatim.
139+
# True if we're handling a multiline else-if condition
140+
my$in_else_if = 0;
141+
# The accumulated line
142+
my$else_if_line;
143+
my$else_if_lineno;
144+
145+
while (<$infh>)
146+
{
147+
chomp;
148+
lastifm|^\s*/\* END GEN_TABCOMPLETE\*/\s*$|;
149+
if ($in_else_if)
150+
{
151+
my$rest =$_;
152+
# collapse leading whitespace
153+
$rest =~s/^\s+//;
154+
$else_if_line .='' .$rest;
155+
# Double right paren is currently sufficient to detect completion
156+
if ($else_if_line =~m/\)\)$/)
157+
{
158+
process_else_if($else_if_line,$else_if_lineno,$.);
159+
$in_else_if = 0;
160+
}
161+
}
162+
elsif (m/^\telse if\(/)
163+
{
164+
$else_if_line =$_;
165+
$else_if_lineno =$.;
166+
# Double right paren is currently sufficient to detect completion
167+
if ($else_if_line =~m/\)\)$/)
168+
{
169+
process_else_if($else_if_line,$else_if_lineno,$.);
170+
}
171+
else
172+
{
173+
$in_else_if = 1;
174+
}
175+
}
176+
else
177+
{
178+
$output_code .=$_ ."\n";
179+
}
180+
}
181+
182+
die"unfinished else-if"if$in_else_if;
183+
184+
# Emit the switch-ending lines.
185+
$output_code .="\tbreak;\n";
186+
$output_code .="\tdefault:\n";
187+
$output_code .="\t\tAssert(false);\n";
188+
$output_code .="\t\tbreak;\n";
189+
$output_code .="\t}\n";
190+
191+
# Keep line numbering in sync.
192+
$next_line_no =$. + 1;
193+
$output_code .="#line${next_line_no}\"tab-complete.in.c\"\n";
194+
195+
# Scan the rest, adding it to $output_code verbatim.
196+
while (<$infh>)
197+
{
198+
chomp;
199+
$output_code .=$_ ."\n";
200+
}
201+
202+
# Dump out the table data.
203+
print$outfh$table_data;
204+
205+
# Dump out the modified code, and we're done!
206+
print$outfh$output_code;
207+
208+
close($infh);
209+
close($outfh);
210+
211+
# Disassemble an else-if condition.
212+
# Add the generated table-contents macro(s) to $table_data,
213+
# and add the replacement case label(s) to $output_code.
214+
subprocess_else_if
215+
{
216+
my ($else_if_line,$else_if_lineno,$end_lineno) =@_;
217+
218+
# Strip the initial "else if (", which we know is there
219+
$else_if_line =~s/^\telse if\(//;
220+
221+
# Handle OR'd conditions
222+
my$isfirst = 1;
223+
while ($else_if_line =~
224+
s/^(Head|Tail|)Matches(CS|)\((("[^"]*"|MatchAnyExcept\("[^"]*"\)|[A-Za-z,\s])+)\)\s*\|\|\s*//
225+
)
226+
{
227+
my$typ =$1;
228+
my$cs =$2;
229+
my$args =$3;
230+
process_match($typ,$cs,$args,$else_if_lineno,$isfirst);
231+
$isfirst = 0;
232+
}
233+
234+
# Check for AND'd condition
235+
if ($else_if_line =~
236+
s/^(Head|Tail|)Matches(CS|)\((("[^"]*"|MatchAnyExcept\("[^"]*"\)|[A-Za-z,\s])+)\)\s*&&\s*//
237+
)
238+
{
239+
my$typ =$1;
240+
my$cs =$2;
241+
my$args =$3;
242+
warn
243+
"could not process OR/ANDed if condition at line$else_if_lineno\n"
244+
if !$isfirst;
245+
process_match($typ,$cs,$args,$else_if_lineno,$isfirst);
246+
$isfirst = 0;
247+
# approximate line positioning of AND'd condition
248+
$output_code .="#line${end_lineno}\"tab-complete.in.c\"\n";
249+
$output_code .="\tif ($else_if_line\n";
250+
}
251+
elsif ($else_if_line =~
252+
s/^(Head|Tail|)Matches(CS|)\((("[^"]*"|MatchAnyExcept\("[^"]*"\)|[A-Za-z,\s])+)\)\)$//
253+
)
254+
{
255+
my$typ =$1;
256+
my$cs =$2;
257+
my$args =$3;
258+
process_match($typ,$cs,$args,$else_if_lineno,$isfirst);
259+
$isfirst = 0;
260+
}
261+
else
262+
{
263+
warn
264+
"could not process if condition at line$else_if_lineno: the rest looks like$else_if_line\n";
265+
$output_code .="\telse if ($else_if_line\n";
266+
}
267+
268+
# Keep line numbering in sync.
269+
if ($end_lineno !=$else_if_lineno)
270+
{
271+
my$next_lineno =$end_lineno + 1;
272+
$output_code .="#line${next_lineno}\"tab-complete.in.c\"\n";
273+
}
274+
}
275+
276+
subprocess_match
277+
{
278+
my ($typ,$cs,$args,$lineno,$isfirst) =@_;
279+
280+
# Assign a new case label only for the first pattern in an OR group.
281+
if ($isfirst)
282+
{
283+
$last_case_label++;
284+
285+
# We intentionally keep the "break;" and the "case" on one line, so
286+
# that they have the same line number as the original "else if"'s
287+
# first line. This avoids misleading displays in, e.g., lcov.
288+
$output_code .="\t";
289+
$output_code .="break;"if$last_case_label > 1;
290+
$output_code .="case$last_case_label:\n";
291+
}
292+
293+
$table_data .=
294+
"\tTCPAT(${last_case_label},${typ}Match${cs},${args}),\n";
295+
}
296+
297+
298+
subusage
299+
{
300+
die<<EOM;
301+
Usage: gen_tabcomplete.pl [--outfile/-o <path>] input_file
302+
--outfile Output file (default is stdout)
303+
304+
gen_tabcomplete.pl transforms tab-complete.in.c to tab-complete.c.
305+
EOM
306+
}

‎src/bin/psql/meson.build

Lines changed: 11 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,6 @@ psql_sources = files(
1313
'prompt.c',
1414
'startup.c',
1515
'stringutils.c',
16-
'tab-complete.c',
1716
'variables.c',
1817
)
1918

@@ -24,6 +23,17 @@ psqlscanslash = custom_target('psqlscanslash',
2423
generated_sources+= psqlscanslash
2524
psql_sources+= psqlscanslash
2625

26+
tabcomplete=custom_target('tabcomplete',
27+
input:'tab-complete.in.c',
28+
output:'tab-complete.c',
29+
command: [
30+
perl,files('gen_tabcomplete.pl'),files('tab-complete.in.c'),
31+
'--outfile','@OUTPUT@','@INPUT@',
32+
],
33+
)
34+
generated_sources+= tabcomplete
35+
psql_sources+= tabcomplete
36+
2737
sql_help=custom_target('psql_help',
2838
output: ['sql_help.c','sql_help.h'],
2939
depfile:'sql_help.dep',

‎src/bin/psql/tab-complete.crenamed to‎src/bin/psql/tab-complete.in.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
*
44
* Copyright (c) 2000-2024, PostgreSQL Global Development Group
55
*
6-
* src/bin/psql/tab-complete.c
6+
* src/bin/psql/tab-complete.in.c
77
*
88
* Note: this will compile and work as-is if SWITCH_CONVERSION_APPLIED
99
* is not defined. However, the expected usage is that it's first run

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