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Commit28a1ae5

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Fix crash in contrib/ltree's lca() function for empty input array.
lca_inner() wasn't prepared for the possibility of getting no inputs.Fix that, and make some cosmetic improvements to the code while at it.Also, I thought the documentation of this function as returning the"longest common prefix" of the paths was entirely misleading; it reallyreturns a path one shorter than the longest common prefix, for the typicaldefinition of "prefix". Don't use that term in the docs, and adjust theexamples to clarify what really happens.This has been broken since its beginning, so back-patch to all supportedbranches.Per report from Hailong Li. Thanks to Pierre Ducroquet for diagnosingand for the initial patch, though I whacked it around some and addedtest cases.Discussion:https://postgr.es/m/5b0d8e4f-f2a3-1305-d612-e00e35a7be66@qunar.com
1 parent333224c commit28a1ae5

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4 files changed

+50
-13
lines changed

4 files changed

+50
-13
lines changed

‎contrib/ltree/expected/ltree.out

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -259,6 +259,24 @@ SELECT lca('{1.2.3,1.2.3.4.5.6}');
259259
1.2
260260
(1 row)
261261

262+
SELECT lca('{1.2.3}');
263+
lca
264+
-----
265+
1.2
266+
(1 row)
267+
268+
SELECT lca('{1}'), lca('{1}') IS NULL;
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lca | ?column?
270+
-----+----------
271+
| f
272+
(1 row)
273+
274+
SELECT lca('{}') IS NULL;
275+
?column?
276+
----------
277+
t
278+
(1 row)
279+
262280
SELECT lca('1.la.2.3','1.2.3.4.5.6');
263281
lca
264282
-----

‎contrib/ltree/ltree_op.c

Lines changed: 25 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -402,22 +402,34 @@ ltree_textadd(PG_FUNCTION_ARGS)
402402
PG_RETURN_POINTER(r);
403403
}
404404

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/*
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* Common code for variants of lca(), find longest common ancestor of inputs
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*
408+
* Returns NULL if there is no common ancestor, ie, the longest common
409+
* prefix is empty.
410+
*/
405411
ltree*
406412
lca_inner(ltree**a,intlen)
407413
{
408414
inttmp,
409-
num= ((*a)->numlevel) ? (*a)->numlevel-1 :0;
410-
ltree**ptr=a+1;
411-
inti,
412-
reslen=LTREE_HDRSIZE;
415+
num,
416+
i,
417+
reslen;
418+
ltree**ptr;
413419
ltree_level*l1,
414420
*l2;
415421
ltree*res;
416422

417-
423+
if (len <=0)
424+
returnNULL;/* no inputs? */
418425
if ((*a)->numlevel==0)
419-
returnNULL;
426+
returnNULL;/* any empty input means NULL result */
427+
428+
/* num is the length of the longest common ancestor so far */
429+
num= (*a)->numlevel-1;
420430

431+
/* Compare each additional input to *a */
432+
ptr=a+1;
421433
while (ptr-a<len)
422434
{
423435
if ((*ptr)->numlevel==0)
@@ -428,11 +440,12 @@ lca_inner(ltree **a, int len)
428440
{
429441
l1=LTREE_FIRST(*a);
430442
l2=LTREE_FIRST(*ptr);
431-
tmp=num;
443+
tmp=Min(num, (*ptr)->numlevel-1);
432444
num=0;
433-
for (i=0;i<Min(tmp, (*ptr)->numlevel-1);i++)
445+
for (i=0;i<tmp;i++)
434446
{
435-
if (l1->len==l2->len&&memcmp(l1->name,l2->name,l1->len)==0)
447+
if (l1->len==l2->len&&
448+
memcmp(l1->name,l2->name,l1->len)==0)
436449
num=i+1;
437450
else
438451
break;
@@ -443,13 +456,16 @@ lca_inner(ltree **a, int len)
443456
ptr++;
444457
}
445458

459+
/* Now compute size of result ... */
460+
reslen=LTREE_HDRSIZE;
446461
l1=LTREE_FIRST(*a);
447462
for (i=0;i<num;i++)
448463
{
449464
reslen+=MAXALIGN(l1->len+LEVEL_HDRSIZE);
450465
l1=LEVEL_NEXT(l1);
451466
}
452467

468+
/* ... and construct it by copying from *a */
453469
res= (ltree*)palloc0(reslen);
454470
SET_VARSIZE(res,reslen);
455471
res->numlevel=num;

‎contrib/ltree/sql/ltree.sql

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -54,6 +54,9 @@ SELECT lca('{la.2.3,1.2.3.4.5.6,""}') IS NULL;
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SELECT lca('{la.2.3,1.2.3.4.5.6}') ISNULL;
5555
SELECT lca('{1.la.2.3,1.2.3.4.5.6}');
5656
SELECT lca('{1.2.3,1.2.3.4.5.6}');
57+
SELECT lca('{1.2.3}');
58+
SELECT lca('{1}'), lca('{1}') ISNULL;
59+
SELECT lca('{}') ISNULL;
5760
SELECT lca('1.la.2.3','1.2.3.4.5.6');
5861
SELECT lca('1.2.3','1.2.3.4.5.6');
5962
SELECT lca('1.2.2.3','1.2.3.4.5.6');

‎doc/src/sgml/ltree.sgml

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -457,17 +457,17 @@ Europe &amp; Russia*@ &amp; !Transportation
457457
<row>
458458
<entry><function>lca(ltree, ltree, ...)</function><indexterm><primary>lca</primary></indexterm></entry>
459459
<entry><type>ltree</type></entry>
460-
<entry>lowest common ancestor, i.e.,longest commonprefix of paths
460+
<entry>longest commonancestor of paths
461461
(up to 8 arguments supported)</entry>
462-
<entry><literal>lca('1.2.2.3','1.2.3.4.5.6')</literal></entry>
462+
<entry><literal>lca('1.2.3','1.2.3.4.5.6')</literal></entry>
463463
<entry><literal>1.2</literal></entry>
464464
</row>
465465

466466
<row>
467467
<entry><function>lca(ltree[])</function></entry>
468468
<entry><type>ltree</type></entry>
469-
<entry>lowest common ancestor, i.e., longest common prefixof paths</entry>
470-
<entry><literal>lca(array['1.2.2.3'::ltree,'1.2.3'])</literal></entry>
469+
<entry>longest common ancestorof paths in array</entry>
470+
<entry><literal>lca(array['1.2.3'::ltree,'1.2.3.4'])</literal></entry>
471471
<entry><literal>1.2</literal></entry>
472472
</row>
473473

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