#include "utils/builtins.h"
-static int
-addone(int *counters, int last, int total)
-{
- /* since this function recurses, it could be driven to stack overflow. */
- check_stack_depth();
-
- counters[last]++;
- if (counters[last] >= total)
- {
- if (last == 0)
- return 0;
- if (addone(counters, last - 1, total - 1) == 0)
- return 0;
- counters[last] = counters[last - 1] + 1;
- }
- return 1;
-}
-
/*
- * If node is equal to ex, replace it with subs. Replacement is actually done
- * by returning either node or a copy of subs.
+ * If "node" is equal to "ex", return a copy of "subs" instead.
+ * If "ex" matches a subset of node's children, return a modified version
+ * of "node" in which those children are replaced with a copy of "subs".
+ * Otherwise return "node" unmodified.
+ *
+ * The QTN_NOCHANGE bit is set in successfully modified nodes, so that
+ * we won't uselessly recurse into them.
+ * Also, set *isfind true if we make a replacement.
*/
static QTNode *
findeq(QTNode *node, QTNode *ex, QTNode *subs, bool *isfind)
{
-
+ /* Can't match unless signature matches and node type matches. */
if ((node->sign & ex->sign) != ex->sign ||
node->valnode->type != ex->valnode->type)
return node;
+ /* Ignore nodes marked NOCHANGE, too. */
if (node->flags & QTN_NOCHANGE)
return node;
if (node->valnode->type == QI_OPR)
{
+ /* Must be same operator. */
if (node->valnode->qoperator.oper != ex->valnode->qoperator.oper)
return node;
if (node->nchild == ex->nchild)
{
+ /*
+ * Simple case: when same number of children, match if equal.
+ * (This is reliable when the children were sorted earlier.)
+ */
if (QTNEq(node, ex))
{
+ /* Match; delete node and return a copy of subs instead. */
QTNFree(node);
if (subs)
{
*isfind = true;
}
}
- else if (node->nchild > ex->nchild)
+ else if (node->nchild > ex->nchild && ex->nchild > 0)
{
/*
- * AND and NOT are commutative, so we check if a subset of the
- * children match. For example, if tnode is A | B | C, and ex is B
- * | C, we have a match after we convert tnode to A | (B | C).
+ * AND and OR are commutative/associative, so we should check if a
+ * subset of the children match. For example, if node is A|B|C,
+ * and ex is B|C, we have a match after we notionally convert node
+ * to A|(B|C). This does not work for NOT or PHRASE nodes, but we
+ * can't get here for those node types because they have a fixed
+ * number of children.
+ *
+ * Because we expect that the children are sorted, it suffices to
+ * make one pass through the two lists to find the matches.
*/
- int *counters = (int *) palloc(sizeof(int) * node->nchild);
- int i;
- QTNode *tnode = (QTNode *) palloc(sizeof(QTNode));
-
- memset(tnode, 0, sizeof(QTNode));
- tnode->child = (QTNode **) palloc(sizeof(QTNode *) * ex->nchild);
- tnode->nchild = ex->nchild;
- tnode->valnode = (QueryItem *) palloc(sizeof(QueryItem));
- *(tnode->valnode) = *(ex->valnode);
-
- for (i = 0; i < ex->nchild; i++)
- counters[i] = i;
-
- do
+ bool *matched;
+ int nmatched;
+ int i,
+ j;
+
+ /* Assert that the subset rule is OK */
+ Assert(node->valnode->qoperator.oper == OP_AND ||
+ node->valnode->qoperator.oper == OP_OR);
+
+ /* matched[] will record which children of node matched */
+ matched = (bool *) palloc0(node->nchild * sizeof(bool));
+ nmatched = 0;
+ i = j = 0;
+ while (i < node->nchild && j < ex->nchild)
{
- tnode->sign = 0;
- for (i = 0; i < ex->nchild; i++)
+ int cmp = QTNodeCompare(node->child[i], ex->child[j]);
+
+ if (cmp == 0)
+ {
+ /* match! */
+ matched[i] = true;
+ nmatched++;
+ i++, j++;
+ }
+ else if (cmp < 0)
{
- tnode->child[i] = node->child[counters[i]];
- tnode->sign |= tnode->child[i]->sign;
+ /* node->child[i] has no match, ignore it */
+ i++;
}
+ else
+ {
+ /* ex->child[j] has no match; we can give up immediately */
+ break;
+ }
+ }
- if (QTNEq(tnode, ex))
+ if (nmatched == ex->nchild)
+ {
+ /* collapse out the matched children of node */
+ j = 0;
+ for (i = 0; i < node->nchild; i++)
{
- int j = 0;
-
- pfree(tnode->valnode);
- pfree(tnode->child);
- pfree(tnode);
- if (subs)
- {
- tnode = QTNCopy(subs);
- tnode->flags = QTN_NOCHANGE | QTN_NEEDFREE;
- }
+ if (matched[i])
+ QTNFree(node->child[i]);
else
- tnode = NULL;
-
- node->child[counters[0]] = tnode;
-
- for (i = 1; i < ex->nchild; i++)
- node->child[counters[i]] = NULL;
- for (i = 0; i < node->nchild; i++)
- {
- if (node->child[i])
- {
- node->child[j] = node->child[i];
- j++;
- }
- }
+ node->child[j++] = node->child[i];
+ }
- node->nchild = j;
+ /* and instead insert a copy of subs */
+ if (subs)
+ {
+ subs = QTNCopy(subs);
+ subs->flags |= QTN_NOCHANGE;
+ node->child[j++] = subs;
+ }
- *isfind = true;
+ node->nchild = j;
+
+ /*
+ * Re-sort the node to put new child in the right place. This
+ * is a bit bogus, because it won't matter for findsubquery's
+ * remaining processing, and it's insufficient to prepare the
+ * tree for another search (we would need to re-flatten as
+ * well, and we don't want to do that because we'd lose the
+ * QTN_NOCHANGE marking on the new child). But it's needed to
+ * keep the results the same as the regression tests expect.
+ */
+ QTNSort(node);
- break;
- }
- } while (addone(counters, ex->nchild - 1, node->nchild));
- if (tnode && (tnode->flags & QTN_NOCHANGE) == 0)
- {
- pfree(tnode->valnode);
- pfree(tnode->child);
- pfree(tnode);
+ *isfind = true;
}
- else
- QTNSort(node);
- pfree(counters);
+
+ pfree(matched);
}
}
else
return node;
}
+/*
+ * Recursive guts of findsubquery(): attempt to replace "ex" with "subs"
+ * at the root node, and if we failed to do so, recursively match against
+ * child nodes.
+ */
static QTNode *
dofindsubquery(QTNode *root, QTNode *ex, QTNode *subs, bool *isfind)
{
/* since this function recurses, it could be driven to stack overflow. */
check_stack_depth();
+ /* also, since it's a bit expensive, let's check for query cancel. */
+ CHECK_FOR_INTERRUPTS();
+
root = findeq(root, ex, subs, isfind);
if (root && (root->flags & QTN_NOCHANGE) == 0 && root->valnode->type == QI_OPR)
return root;
}
+/*
+ * Delete any void subtrees that may have been inserted when the replacement
+ * subtree is void.
+ */
static QTNode *
dropvoidsubtree(QTNode *root)
{
-
if (!root)
return NULL;
return root;
}
+/*
+ * Substitute "subs" for "ex" throughout the QTNode tree at root.
+ *
+ * If isfind isn't NULL, set *isfind to show whether we made any substitution.
+ *
+ * Both "root" and "ex" must have been through QTNTernary and QTNSort
+ * to ensure reliable matching.
+ */
QTNode *
findsubquery(QTNode *root, QTNode *ex, QTNode *subs, bool *isfind)
{
{
/* ready the tree for another pass */
QTNClearFlags(tree, QTN_NOCHANGE);
+ QTNTernary(tree);
QTNSort(tree);
}
}
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