}
-#ifdef V_UNKNOWN /* exists in Windows headers */
-#undef V_UNKNOWN
-#endif
-#ifdef V_FALSE /* exists in Solaris headers */
-#undef V_FALSE
-#endif
-
-/*
- * output values for result output parameter of clean_fakeval_intree
- */
-#define V_UNKNOWN 0 /* the expression can't be evaluated
- * statically */
-#define V_TRUE 1 /* the expression is always true (not
- * implemented) */
-#define V_FALSE 2 /* the expression is always false (not
- * implemented) */
-#define V_STOP 3 /* the expression is a stop word */
-
/*
- * Remove QI_VALSTOP (stopword nodes) from query tree.
+ * Remove QI_VALSTOP (stopword) nodes from query tree.
+ *
+ * Returns NULL if the query degenerates to nothing. Input must not be NULL.
+ *
+ * When we remove a phrase operator due to removing one or both of its
+ * arguments, we might need to adjust the distance of a parent phrase
+ * operator. For example, 'a' is a stopword, so:
+ * (b <-> a) <-> c should become b <2> c
+ * b <-> (a <-> c) should become b <2> c
+ * (b <-> (a <-> a)) <-> c should become b <3> c
+ * b <-> ((a <-> a) <-> c) should become b <3> c
+ * To handle that, we define two output parameters:
+ * ladd: amount to add to a phrase distance to the left of this node
+ * radd: amount to add to a phrase distance to the right of this node
+ * We need two outputs because we could need to bubble up adjustments to two
+ * different parent phrase operators. Consider
+ * w <-> (((a <-> x) <2> (y <3> a)) <-> z)
+ * After we've removed the two a's and are considering the <2> node (which is
+ * now just x <2> y), we have an ladd distance of 1 that needs to propagate
+ * up to the topmost (leftmost) <->, and an radd distance of 3 that needs to
+ * propagate to the rightmost <->, so that we'll end up with
+ * w <2> ((x <2> y) <4> z)
+ * Near the bottom of the tree, we may have subtrees consisting only of
+ * stopwords. The distances of any phrase operators within such a subtree are
+ * summed and propagated to both ladd and radd, since we don't know which side
+ * of the lowest surviving phrase operator we are in. The rule is that any
+ * subtree that degenerates to NULL must return equal values of ladd and radd,
+ * and the parent node dealing with it should incorporate only one of those.
+ *
+ * Currently, we only implement this adjustment for adjacent phrase operators.
+ * Thus for example 'x <-> ((a <-> y) | z)' will become 'x <-> (y | z)', which
+ * isn't ideal, but there is no way to represent the really desired semantics
+ * without some redesign of the tsquery structure. Certainly it would not be
+ * any better to convert that to 'x <2> (y | z)'. Since this is such a weird
+ * corner case, let it go for now. But we can fix it in cases where the
+ * intervening non-phrase operator also gets removed, for example
+ * '((x <-> a) | a) <-> y' will become 'x <2> y'.
*/
static NODE *
-clean_fakeval_intree(NODE *node, char *result, int *adddistance)
+clean_stopword_intree(NODE *node, int *ladd, int *radd)
{
- char lresult = V_UNKNOWN,
- rresult = V_UNKNOWN;
-
/* since this function recurses, it could be driven to stack overflow. */
check_stack_depth();
- if (adddistance)
- *adddistance = 0;
+ /* default output parameters indicate no change in parent distance */
+ *ladd = *radd = 0;
if (node->valnode->type == QI_VAL)
return node;
else if (node->valnode->type == QI_VALSTOP)
{
pfree(node);
- *result = V_STOP;
return NULL;
}
if (node->valnode->qoperator.oper == OP_NOT)
{
- node->right = clean_fakeval_intree(node->right, &rresult, NULL);
+ /* NOT doesn't change pattern width, so just report child distances */
+ node->right = clean_stopword_intree(node->right, ladd, radd);
if (!node->right)
{
- *result = V_STOP;
freetree(node);
return NULL;
}
else
{
NODE *res = node;
+ bool isphrase;
int ndistance,
- ldistance = 0,
- rdistance = 0;
+ lladd,
+ lradd,
+ rladd,
+ rradd;
- ndistance = (node->valnode->qoperator.oper == OP_PHRASE) ?
- node->valnode->qoperator.distance :
- 0;
+ /* First, recurse */
+ node->left = clean_stopword_intree(node->left, &lladd, &lradd);
+ node->right = clean_stopword_intree(node->right, &rladd, &rradd);
- node->left = clean_fakeval_intree(node->left,
- &lresult,
- ndistance ? &ldistance : NULL);
+ /* Check if current node is OP_PHRASE, get its distance */
+ isphrase = (node->valnode->qoperator.oper == OP_PHRASE);
+ ndistance = isphrase ? node->valnode->qoperator.distance : 0;
- node->right = clean_fakeval_intree(node->right,
- &rresult,
- ndistance ? &rdistance : NULL);
-
- /*
- * ndistance, ldistance and rdistance are greater than zero if their
- * corresponding nodes are OP_PHRASE
- */
-
- if (lresult == V_STOP && rresult == V_STOP)
+ if (node->left == NULL && node->right == NULL)
{
- if (adddistance && ndistance)
- *adddistance = ldistance + ndistance + rdistance;
+ /*
+ * When we collapse out a phrase node entirely, propagate its own
+ * distance into both *ladd and *radd; it is the responsibility of
+ * the parent node to count it only once. Also, for a phrase
+ * node, distances coming from children are summed and propagated
+ * up to parent (we assume lladd == lradd and rladd == rradd, else
+ * rule was broken at a lower level). But if this isn't a phrase
+ * node, take the larger of the two child distances; that
+ * corresponds to what TS_execute will do in non-stopword cases.
+ */
+ if (isphrase)
+ *ladd = *radd = lladd + ndistance + rladd;
+ else
+ *ladd = *radd = Max(lladd, rladd);
freetree(node);
- *result = V_STOP;
return NULL;
}
- else if (lresult == V_STOP)
+ else if (node->left == NULL)
{
+ /* Removing this operator and left subnode */
+ /* lladd and lradd are equal/redundant, don't count both */
+ if (isphrase)
+ {
+ /* operator's own distance must propagate to left */
+ *ladd = lladd + ndistance + rladd;
+ *radd = rradd;
+ }
+ else
+ {
+ /* at non-phrase op, just forget the left subnode entirely */
+ *ladd = rladd;
+ *radd = rradd;
+ }
res = node->right;
-
- /*
- * propagate distance from current node to the right upper
- * subtree.
- */
- if (adddistance && ndistance)
- *adddistance = rdistance;
pfree(node);
}
- else if (rresult == V_STOP)
+ else if (node->right == NULL)
{
+ /* Removing this operator and right subnode */
+ /* rladd and rradd are equal/redundant, don't count both */
+ if (isphrase)
+ {
+ /* operator's own distance must propagate to right */
+ *ladd = lladd;
+ *radd = lradd + ndistance + rradd;
+ }
+ else
+ {
+ /* at non-phrase op, just forget the right subnode entirely */
+ *ladd = lladd;
+ *radd = lradd;
+ }
res = node->left;
-
- /*
- * propagate distance from current node to the upper tree.
- */
- if (adddistance && ndistance)
- *adddistance = ndistance + ldistance;
pfree(node);
}
- else if (ndistance)
+ else if (isphrase)
{
- node->valnode->qoperator.distance += ldistance;
- if (adddistance)
- *adddistance = 0;
+ /* Absorb appropriate corrections at this level */
+ node->valnode->qoperator.distance += lradd + rladd;
+ /* Propagate up any unaccounted-for corrections */
+ *ladd = lladd;
+ *radd = rradd;
}
- else if (adddistance)
+ else
{
- *adddistance = 0;
+ /* We're keeping a non-phrase operator, so ladd/radd remain 0 */
}
return res;
commonlen,
i;
NODE *root;
- char result = V_UNKNOWN;
+ int ladd,
+ radd;
TSQuery out;
QueryItem *items;
char *operands;
return in;
/* eliminate stop words */
- root = clean_fakeval_intree(maketree(GETQUERY(in)), &result, NULL);
- if (result != V_UNKNOWN)
+ root = clean_stopword_intree(maketree(GETQUERY(in)), &ladd, &radd);
+ if (root == NULL)
{
ereport(NOTICE,
(errmsg("text-search query contains only stop words or doesn't contain lexemes, ignored")));
projects / postgresql / commitdiff