Stephen Frost <sfr...@snowman.net> writes:
> * Tom Lane (t...@sss.pgh.pa.us) wrote:
>> Stephen Frost <sfr...@snowman.net> writes:
>>> * Tom Lane (t...@sss.pgh.pa.us) wrote:
>>>> We could hard-code a rule like that, or we could introduce a new
>>>> explicit parameter for the maximum cover length. The latter would be
>>>> more flexible, but we need something back-patchable and I'm concerned
>>>> about the compatibility hazards of adding a new parameter in minor
>>>> releases. So on the whole I propose hard-wiring a multiplier of,
>>>> say, 10 for both these cases.
>>> That sounds alright to me, though I do think we should probably still
>>> toss a CFI (or two) in this path somewhere as we don't know how long
>>> some of these functions might take...
>> Yeah, of course. I'm still leaning to doing that in TS_execute_recurse.
> Works for me.
Here's a proposed patch along that line.
regards, tom lane
diff --git a/src/backend/tsearch/wparser_def.c b/src/backend/tsearch/wparser_def.c
index 76b6f9aef0..1df1c0362d 100644
--- a/src/backend/tsearch/wparser_def.c
+++ b/src/backend/tsearch/wparser_def.c
@@ -2028,8 +2028,10 @@ hlFirstIndex(HeadlineParsedText *prs, TSQuery query, int pos)
/*
* hlCover: try to find a substring of prs' word list that satisfies query
*
- * At entry, *p must be the first word index to consider (initialize this to
- * zero, or to the next index after a previous successful search).
+ * At entry, *p must be the first word index to consider (initialize this
+ * to zero, or to the next index after a previous successful search).
+ * We will consider all substrings starting at or after that word, and
+ * containing no more than max_cover words.
*
* On success, sets *p to first word index and *q to last word index of the
* cover substring, and returns true.
@@ -2038,7 +2040,8 @@ hlFirstIndex(HeadlineParsedText *prs, TSQuery query, int pos)
* words used in the query.
*/
static bool
-hlCover(HeadlineParsedText *prs, TSQuery query, int *p, int *q)
+hlCover(HeadlineParsedText *prs, TSQuery query, int max_cover,
+ int *p, int *q)
{
int pmin,
pmax,
@@ -2084,7 +2087,7 @@ hlCover(HeadlineParsedText *prs, TSQuery query, int *p, int *q)
nextpmin = nextpmax;
pmax = nextpmax;
}
- while (pmax >= 0);
+ while (pmax >= 0 && pmax - pmin < max_cover);
/* No luck here, so try next feasible startpoint */
pmin = nextpmin;
}
@@ -2186,7 +2189,7 @@ get_next_fragment(HeadlineParsedText *prs, int *startpos, int *endpos,
static void
mark_hl_fragments(HeadlineParsedText *prs, TSQuery query, bool highlightall,
int shortword, int min_words,
- int max_words, int max_fragments)
+ int max_words, int max_fragments, int max_cover)
{
int32 poslen,
curlen,
@@ -2213,7 +2216,7 @@ mark_hl_fragments(HeadlineParsedText *prs, TSQuery query, bool highlightall,
covers = palloc(maxcovers * sizeof(CoverPos));
/* get all covers */
- while (hlCover(prs, query, &p, &q))
+ while (hlCover(prs, query, max_cover, &p, &q))
{
startpos = p;
endpos = q;
@@ -2368,7 +2371,7 @@ mark_hl_fragments(HeadlineParsedText *prs, TSQuery query, bool highlightall,
*/
static void
mark_hl_words(HeadlineParsedText *prs, TSQuery query, bool highlightall,
- int shortword, int min_words, int max_words)
+ int shortword, int min_words, int max_words, int max_cover)
{
int p = 0,
q = 0;
@@ -2386,7 +2389,7 @@ mark_hl_words(HeadlineParsedText *prs, TSQuery query, bool highlightall,
if (!highlightall)
{
/* examine all covers, select a headline using the best one */
- while (hlCover(prs, query, &p, &q))
+ while (hlCover(prs, query, max_cover, &p, &q))
{
/*
* Count words (curlen) and interesting words (poslen) within
@@ -2542,6 +2545,7 @@ prsd_headline(PG_FUNCTION_ARGS)
int shortword = 3;
int max_fragments = 0;
bool highlightall = false;
+ int max_cover;
ListCell *l;
/* Extract configuration option values */
@@ -2581,6 +2585,15 @@ prsd_headline(PG_FUNCTION_ARGS)
defel->defname)));
}
+ /*
+ * We might eventually make max_cover a user-settable parameter, but for
+ * now, just compute a reasonable value based on max_words and
+ * max_fragments.
+ */
+ max_cover = Max(max_words * 10, 100);
+ if (max_fragments > 0)
+ max_cover *= max_fragments;
+
/* in HighlightAll mode these parameters are ignored */
if (!highlightall)
{
@@ -2605,10 +2618,10 @@ prsd_headline(PG_FUNCTION_ARGS)
/* Apply appropriate headline selector */
if (max_fragments == 0)
mark_hl_words(prs, query, highlightall, shortword,
- min_words, max_words);
+ min_words, max_words, max_cover);
else
mark_hl_fragments(prs, query, highlightall, shortword,
- min_words, max_words, max_fragments);
+ min_words, max_words, max_fragments, max_cover);
/* Fill in default values for string options */
if (!prs->startsel)
diff --git a/src/backend/utils/adt/tsvector_op.c b/src/backend/utils/adt/tsvector_op.c
index f01b1ee253..756a48a167 100644
--- a/src/backend/utils/adt/tsvector_op.c
+++ b/src/backend/utils/adt/tsvector_op.c
@@ -1868,6 +1868,9 @@ TS_execute_recurse(QueryItem *curitem, void *arg, uint32 flags,
/* since this function recurses, it could be driven to stack overflow */
check_stack_depth();
+ /* ... and let's check for query cancel while we're at it */
+ CHECK_FOR_INTERRUPTS();
+
if (curitem->type == QI_VAL)
return chkcond(arg, (QueryOperand *) curitem,
NULL /* don't need position info */ );
