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Teach psql to show the location of syntax errors visually, per recent
discussions. Patch by Fabien Coelho and Tom Lane. Still needs to be taught about multi-screen-column kanji characters; Tatsuo has promised to provide the needed infrastructure for that.
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‎src/bin/psql/common.c

+215-4
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
*
44
* Copyright (c) 2000-2003, PostgreSQL Global Development Group
55
*
6-
* $PostgreSQL: pgsql/src/bin/psql/common.c,v 1.82 2004/01/25 03:07:22 neilc Exp $
6+
* $PostgreSQL: pgsql/src/bin/psql/common.c,v 1.83 2004/03/14 04:25:17 tgl Exp $
77
*/
88
#include "postgres_fe.h"
99
#include "common.h"
@@ -345,6 +345,216 @@ ResetCancelConn(void)
345345
}
346346

347347

348+
/*
349+
* on errors, print syntax error position if available.
350+
*
351+
* the query is expected to be in the client encoding.
352+
*/
353+
static void
354+
ReportSyntaxErrorPosition(const PGresult *result, const char *query)
355+
{
356+
#define DISPLAY_SIZE 60 /* screen width limit, in screen cols */
357+
#define MIN_RIGHT_CUT 10 /* try to keep this far away from EOL */
358+
359+
int loc = 0;
360+
const char *sp;
361+
int clen, slen, i, *qidx, *scridx, qoffset, scroffset, ibeg, iend,
362+
loc_line;
363+
char *wquery;
364+
bool beg_trunc, end_trunc;
365+
PQExpBufferData msg;
366+
367+
if (query == NULL)
368+
return; /* nothing to do */
369+
sp = PQresultErrorField(result, PG_DIAG_STATEMENT_POSITION);
370+
if (sp == NULL)
371+
return; /* no syntax error location */
372+
/*
373+
* We punt if the report contains any CONTEXT. This typically means that
374+
* the syntax error is from inside a function, and the cursor position
375+
* is not relevant to the original query string.
376+
*/
377+
if (PQresultErrorField(result, PG_DIAG_CONTEXT) != NULL)
378+
return;
379+
380+
if (sscanf(sp, "%d", &loc) != 1)
381+
{
382+
psql_error("INTERNAL ERROR: unexpected statement position \"%s\"\n",
383+
sp);
384+
return;
385+
}
386+
387+
/* Make a writable copy of the query, and a buffer for messages. */
388+
wquery = pg_strdup(query);
389+
390+
initPQExpBuffer(&msg);
391+
392+
/*
393+
* The returned cursor position is measured in logical characters.
394+
* Each character might occupy multiple physical bytes in the string,
395+
* and in some Far Eastern character sets it might take more than one
396+
* screen column as well. We compute the starting byte offset and
397+
* starting screen column of each logical character, and store these
398+
* in qidx[] and scridx[] respectively.
399+
*/
400+
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/* we need a safe allocation size... */
402+
slen = strlen(query) + 1;
403+
404+
qidx = (int *) pg_malloc(slen * sizeof(int));
405+
scridx = (int *) pg_malloc(slen * sizeof(int));
406+
407+
qoffset = 0;
408+
scroffset = 0;
409+
for (i = 0; query[qoffset] != '\0'; i++)
410+
{
411+
qidx[i] = qoffset;
412+
scridx[i] = scroffset;
413+
scroffset += 1; /* XXX fix me when we have screen width info */
414+
qoffset += PQmblen(&query[qoffset], pset.encoding);
415+
}
416+
qidx[i] = qoffset;
417+
scridx[i] = scroffset;
418+
clen = i;
419+
psql_assert(clen < slen);
420+
421+
/* convert loc to zero-based offset in qidx/scridx arrays */
422+
loc--;
423+
424+
/* do we have something to show? */
425+
if (loc >= 0 && loc <= clen)
426+
{
427+
/* input line number of our syntax error. */
428+
loc_line = 1;
429+
/* first included char of extract. */
430+
ibeg = 0;
431+
/* last-plus-1 included char of extract. */
432+
iend = clen;
433+
434+
/*
435+
* Replace tabs with spaces in the writable copy. (Later we might
436+
* want to think about coping with their variable screen width,
437+
* but not today.)
438+
*
439+
* Extract line number and begin and end indexes of line containing
440+
* error location. There will not be any newlines or carriage
441+
* returns in the selected extract.
442+
*/
443+
for (i=0; i<clen; i++)
444+
{
445+
/* character length must be 1 or it's not ASCII */
446+
if ((qidx[i+1]-qidx[i]) == 1)
447+
{
448+
if (wquery[qidx[i]] == '\t')
449+
wquery[qidx[i]] = ' ';
450+
else if (wquery[qidx[i]] == '\r' || wquery[qidx[i]] == '\n')
451+
{
452+
if (i < loc)
453+
{
454+
/*
455+
* count lines before loc. Each \r or \n counts
456+
* as a line except when \r \n appear together.
457+
*/
458+
if (wquery[qidx[i]] == '\r' ||
459+
i == 0 ||
460+
(qidx[i]-qidx[i-1]) != 1 ||
461+
wquery[qidx[i-1]] != '\r')
462+
loc_line++;
463+
/* extract beginning = last line start before loc. */
464+
ibeg = i+1;
465+
}
466+
else
467+
{
468+
/* set extract end. */
469+
iend = i;
470+
/* done scanning. */
471+
break;
472+
}
473+
}
474+
}
475+
}
476+
477+
/* If the line extracted is too long, we truncate it. */
478+
beg_trunc = false;
479+
end_trunc = false;
480+
if (scridx[iend]-scridx[ibeg] > DISPLAY_SIZE)
481+
{
482+
/*
483+
* We first truncate right if it is enough. This code might
484+
* be off a space or so on enforcing MIN_RIGHT_CUT if there's
485+
* a wide character right there, but that should be okay.
486+
*/
487+
if (scridx[ibeg]+DISPLAY_SIZE >= scridx[loc]+MIN_RIGHT_CUT)
488+
{
489+
while (scridx[iend]-scridx[ibeg] > DISPLAY_SIZE)
490+
iend--;
491+
end_trunc = true;
492+
}
493+
else
494+
{
495+
/* Truncate right if not too close to loc. */
496+
while (scridx[loc]+MIN_RIGHT_CUT < scridx[iend])
497+
{
498+
iend--;
499+
end_trunc = true;
500+
}
501+
502+
/* Truncate left if still too long. */
503+
while (scridx[iend]-scridx[ibeg] > DISPLAY_SIZE)
504+
{
505+
ibeg++;
506+
beg_trunc = true;
507+
}
508+
}
509+
}
510+
511+
/* the extract MUST contain the target position! */
512+
psql_assert(ibeg<=loc && loc<=iend);
513+
514+
/* truncate working copy at desired endpoint */
515+
wquery[qidx[iend]] = '\0';
516+
517+
/* Begin building the finished message. */
518+
printfPQExpBuffer(&msg, gettext("LINE %d: "), loc_line);
519+
if (beg_trunc)
520+
appendPQExpBufferStr(&msg, "...");
521+
522+
/*
523+
* While we have the prefix in the msg buffer, compute its screen
524+
* width.
525+
*/
526+
scroffset = 0;
527+
for (i = 0; i < msg.len; i += PQmblen(&msg.data[i], pset.encoding))
528+
{
529+
scroffset += 1; /* XXX fix me when we have screen width info */
530+
}
531+
532+
/* Finish and emit the message. */
533+
appendPQExpBufferStr(&msg, &wquery[qidx[ibeg]]);
534+
if (end_trunc)
535+
appendPQExpBufferStr(&msg, "...");
536+
537+
psql_error("%s\n", msg.data);
538+
539+
/* Now emit the cursor marker line. */
540+
scroffset += scridx[loc] - scridx[ibeg];
541+
resetPQExpBuffer(&msg);
542+
for (i = 0; i < scroffset; i++)
543+
appendPQExpBufferChar(&msg, ' ');
544+
appendPQExpBufferChar(&msg, '^');
545+
546+
psql_error("%s\n", msg.data);
547+
}
548+
549+
/* Clean up. */
550+
termPQExpBuffer(&msg);
551+
552+
free(wquery);
553+
free(qidx);
554+
free(scridx);
555+
}
556+
557+
348558
/*
349559
* AcceptResult
350560
*
@@ -355,7 +565,7 @@ ResetCancelConn(void)
355565
* Returns true for valid result, false for error state.
356566
*/
357567
static bool
358-
AcceptResult(const PGresult *result)
568+
AcceptResult(const PGresult *result, const char *query)
359569
{
360570
bool OK = true;
361571

@@ -386,6 +596,7 @@ AcceptResult(const PGresult *result)
386596
if (!OK)
387597
{
388598
psql_error("%s", PQerrorMessage(pset.db));
599+
ReportSyntaxErrorPosition(result, query);
389600
CheckConnection();
390601
}
391602

@@ -449,7 +660,7 @@ PSQLexec(const char *query, bool start_xact)
449660

450661
res = PQexec(pset.db, query);
451662

452-
if (!AcceptResult(res) && res)
663+
if (!AcceptResult(res, query) && res)
453664
{
454665
PQclear(res);
455666
res = NULL;
@@ -695,7 +906,7 @@ SendQuery(const char *query)
695906
results = PQexec(pset.db, query);
696907

697908
/* these operations are included in the timing result: */
698-
OK = (AcceptResult(results) && ProcessCopyResult(results));
909+
OK = (AcceptResult(results, query) && ProcessCopyResult(results));
699910

700911
if (pset.timing)
701912
GETTIMEOFDAY(&after);

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