From 28a1ae5342fe39b7c4057d3f872cb6057f5f33bf Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 13 Jul 2018 18:45:30 -0400 Subject: [PATCH] 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 really returns a path one shorter than the longest common prefix, for the typical definition of "prefix". Don't use that term in the docs, and adjust the examples to clarify what really happens. This has been broken since its beginning, so back-patch to all supported branches. Per report from Hailong Li. Thanks to Pierre Ducroquet for diagnosing and for the initial patch, though I whacked it around some and added test cases. Discussion: https://postgr.es/m/5b0d8e4f-f2a3-1305-d612-e00e35a7be66@qunar.com --- contrib/ltree/expected/ltree.out | 18 +++++++++++++++++ contrib/ltree/ltree_op.c | 34 +++++++++++++++++++++++--------- contrib/ltree/sql/ltree.sql | 3 +++ doc/src/sgml/ltree.sgml | 8 ++++---- 4 files changed, 50 insertions(+), 13 deletions(-) diff --git a/contrib/ltree/expected/ltree.out b/contrib/ltree/expected/ltree.out index 3d5737d41b..8226930905 100644 --- a/contrib/ltree/expected/ltree.out +++ b/contrib/ltree/expected/ltree.out @@ -259,6 +259,24 @@ SELECT lca('{1.2.3,1.2.3.4.5.6}'); 1.2 (1 row) +SELECT lca('{1.2.3}'); + lca +----- + 1.2 +(1 row) + +SELECT lca('{1}'), lca('{1}') IS NULL; + lca | ?column? +-----+---------- + | f +(1 row) + +SELECT lca('{}') IS NULL; + ?column? +---------- + t +(1 row) + SELECT lca('1.la.2.3','1.2.3.4.5.6'); lca ----- diff --git a/contrib/ltree/ltree_op.c b/contrib/ltree/ltree_op.c index d62ca02521..759f1f8d29 100644 --- a/contrib/ltree/ltree_op.c +++ b/contrib/ltree/ltree_op.c @@ -402,22 +402,34 @@ ltree_textadd(PG_FUNCTION_ARGS) PG_RETURN_POINTER(r); } +/* + * Common code for variants of lca(), find longest common ancestor of inputs + * + * Returns NULL if there is no common ancestor, ie, the longest common + * prefix is empty. + */ ltree * lca_inner(ltree **a, int len) { int tmp, - num = ((*a)->numlevel) ? (*a)->numlevel - 1 : 0; - ltree **ptr = a + 1; - int i, - reslen = LTREE_HDRSIZE; + num, + i, + reslen; + ltree **ptr; ltree_level *l1, *l2; ltree *res; - + if (len <= 0) + return NULL; /* no inputs? */ if ((*a)->numlevel == 0) - return NULL; + return NULL; /* any empty input means NULL result */ + /* num is the length of the longest common ancestor so far */ + num = (*a)->numlevel - 1; + + /* Compare each additional input to *a */ + ptr = a + 1; while (ptr - a < len) { if ((*ptr)->numlevel == 0) @@ -428,11 +440,12 @@ lca_inner(ltree **a, int len) { l1 = LTREE_FIRST(*a); l2 = LTREE_FIRST(*ptr); - tmp = num; + tmp = Min(num, (*ptr)->numlevel - 1); num = 0; - for (i = 0; i < Min(tmp, (*ptr)->numlevel - 1); i++) + for (i = 0; i < tmp; i++) { - if (l1->len == l2->len && memcmp(l1->name, l2->name, l1->len) == 0) + if (l1->len == l2->len && + memcmp(l1->name, l2->name, l1->len) == 0) num = i + 1; else break; @@ -443,6 +456,8 @@ lca_inner(ltree **a, int len) ptr++; } + /* Now compute size of result ... */ + reslen = LTREE_HDRSIZE; l1 = LTREE_FIRST(*a); for (i = 0; i < num; i++) { @@ -450,6 +465,7 @@ lca_inner(ltree **a, int len) l1 = LEVEL_NEXT(l1); } + /* ... and construct it by copying from *a */ res = (ltree *) palloc0(reslen); SET_VARSIZE(res, reslen); res->numlevel = num; diff --git a/contrib/ltree/sql/ltree.sql b/contrib/ltree/sql/ltree.sql index e9f74909a6..846b04e48e 100644 --- a/contrib/ltree/sql/ltree.sql +++ b/contrib/ltree/sql/ltree.sql @@ -54,6 +54,9 @@ SELECT lca('{la.2.3,1.2.3.4.5.6,""}') IS NULL; SELECT lca('{la.2.3,1.2.3.4.5.6}') IS NULL; SELECT lca('{1.la.2.3,1.2.3.4.5.6}'); SELECT lca('{1.2.3,1.2.3.4.5.6}'); +SELECT lca('{1.2.3}'); +SELECT lca('{1}'), lca('{1}') IS NULL; +SELECT lca('{}') IS NULL; SELECT lca('1.la.2.3','1.2.3.4.5.6'); SELECT lca('1.2.3','1.2.3.4.5.6'); SELECT lca('1.2.2.3','1.2.3.4.5.6'); diff --git a/doc/src/sgml/ltree.sgml b/doc/src/sgml/ltree.sgml index 98e0ca5c62..3ddd335b8c 100644 --- a/doc/src/sgml/ltree.sgml +++ b/doc/src/sgml/ltree.sgml @@ -457,17 +457,17 @@ Europe & Russia*@ & !Transportation lca(ltree, ltree, ...)lca ltree - lowest common ancestor, i.e., longest common prefix of paths + longest common ancestor of paths (up to 8 arguments supported) - lca('1.2.2.3','1.2.3.4.5.6') + lca('1.2.3','1.2.3.4.5.6') 1.2 lca(ltree[]) ltree - lowest common ancestor, i.e., longest common prefix of paths - lca(array['1.2.2.3'::ltree,'1.2.3']) + longest common ancestor of paths in array + lca(array['1.2.3'::ltree,'1.2.3.4']) 1.2