Start Reimplementing MERGE Clause

Author: JoshInnis

Makefile

@@ -26,6 +26,7 @@ OBJS = src/backend/postgraph.o \
        src/backend/commands/graph_commands.o \
        src/backend/commands/label_commands.o \
        src/backend/executor/cypher_create.o \
+       src/backend/executor/cypher_merge.o \
        src/backend/nodes/ag_nodes.o \
        src/backend/nodes/cypher_copyfuncs.o \
        src/backend/nodes/cypher_outfuncs.o \
@@ -68,7 +69,8 @@ EXTENSION = postgraph
 DATA = postgraph--0.1.0.sql
 
 REGRESS = new_cypher \
-          cypher_create
+          cypher_create \
+          cypher_merge
 
 srcdir=`pwd`
 POSTGIS_DIR ?= postgis_dir

src/backend/optimizer/cypher_createplan.c

@@ -29,7 +29,8 @@
 
 const CustomScanMethods cypher_create_plan_methods = {
     "Cypher Create", create_cypher_create_plan_state};
-
+const CustomScanMethods cypher_merge_plan_methods = {
+    "Cypher Merge", create_cypher_merge_plan_state};
 
 Plan *plan_cypher_create_path(PlannerInfo *root, RelOptInfo *rel,
                               CustomPath *best_path, List *tlist,
@@ -72,3 +73,64 @@ Plan *plan_cypher_create_path(PlannerInfo *root, RelOptInfo *rel,
 
     return (Plan *)cs;
 }
+
+/*
+ * Coverts the Scan node representing the delete clause
+ * to the merge Plan node
+ */
+Plan *plan_cypher_merge_path(PlannerInfo *root, RelOptInfo *rel,
+                           CustomPath *best_path, List *tlist,
+                           List *clauses, List *custom_plans)
+{
+    CustomScan *cs;
+    Plan *subplan = linitial(custom_plans);
+
+    cs = makeNode(CustomScan);
+
+    cs->scan.plan.startup_cost = best_path->path.startup_cost;
+    cs->scan.plan.total_cost = best_path->path.total_cost;
+
+    cs->scan.plan.plan_rows = best_path->path.rows;
+    cs->scan.plan.plan_width = 0;
+
+    cs->scan.plan.parallel_aware = best_path->path.parallel_aware;
+    cs->scan.plan.parallel_safe = best_path->path.parallel_safe;
+
+    cs->scan.plan.plan_node_id = 0; // Set later in set_plan_refs
+    /*
+     * the scan list of the delete node, used for its ScanTupleSlot used
+     * by its parent in the execution phase.
+     */
+    cs->scan.plan.targetlist = tlist;
+    cs->scan.plan.qual = NIL;
+    cs->scan.plan.lefttree = NULL;
+    cs->scan.plan.righttree = NULL;
+    cs->scan.plan.initPlan = NIL;
+
+    cs->scan.plan.extParam = NULL;
+    cs->scan.plan.allParam = NULL;
+
+    /*
+     * We do not want Postgres to assume we are scanning a table, postgres'
+     * optimizer will make assumptions about our targetlist that are false
+     */
+    cs->scan.scanrelid = 0;
+
+    cs->flags = best_path->flags;
+
+    // child plan nodes are here, Postgres processed them for us.
+    cs->custom_plans = custom_plans;
+    cs->custom_exprs = NIL;
+    // transfer delete metadata needed by the delete clause.
+    cs->custom_private = best_path->custom_private;
+    /*
+     * the scan list of the merge node's children, used for ScanTupleSlot
+     * in execution.
+     */
+    cs->custom_scan_tlist = subplan->targetlist;
+
+    cs->custom_relids = NULL;
+    cs->methods = &cypher_merge_plan_methods;
+
+    return (Plan *)cs;
+}

src/backend/optimizer/cypher_pathnode.c

@@ -28,7 +28,8 @@
 
 const CustomPathMethods cypher_create_path_methods = {
     CREATE_PATH_NAME, plan_cypher_create_path, NULL};
-
+const CustomPathMethods cypher_merge_path_methods = {
+    MERGE_PATH_NAME, plan_cypher_merge_path, NULL};
 
 CustomPath *create_cypher_create_path(PlannerInfo *root, RelOptInfo *rel,
                                       List *custom_private)
@@ -65,3 +66,46 @@ CustomPath *create_cypher_create_path(PlannerInfo *root, RelOptInfo *rel,
 
     return cp;
 }
+
+/*
+ * Creates a Delete Path. Makes the original path a child of the new
+ * path. We leave it to the caller to replace the pathlist of the rel.
+ */
+CustomPath *create_cypher_merge_path(PlannerInfo *root, RelOptInfo *rel,
+                                   List *custom_private)
+{
+    CustomPath *cp;
+
+    cp = makeNode(CustomPath);
+
+    cp->path.pathtype = T_CustomScan;
+
+    cp->path.parent = rel;
+    cp->path.pathtarget = rel->reltarget;
+
+    cp->path.param_info = NULL;
+
+    // Do not allow parallel methods
+    cp->path.parallel_aware = false;
+    cp->path.parallel_safe = false;
+    cp->path.parallel_workers = 0;
+
+    cp->path.rows = 0;
+    cp->path.startup_cost = 0;
+    cp->path.total_cost = 0;
+
+    // No output ordering for basic SET
+    cp->path.pathkeys = NULL;
+
+    // Disable all custom flags for now
+    cp->flags = 0;
+
+    // Make the original paths the children of the new path
+    cp->custom_paths = rel->pathlist;
+    // Store the metadata Delete will need in the execution phase.
+    cp->custom_private = custom_private;
+    // Tells Postgres how to turn this path to the correct CustomScan
+    cp->methods = &cypher_merge_path_methods;
+
+    return cp;
+}

src/backend/optimizer/cypher_paths.c

@@ -44,7 +44,8 @@ static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, Index rti,
 static cypher_clause_kind get_cypher_clause_kind(RangeTblEntry *rte);
 static void handle_cypher_create_clause(PlannerInfo *root, RelOptInfo *rel,
                                         Index rti, RangeTblEntry *rte);
-
+static void handle_cypher_merge_clause(PlannerInfo *root, RelOptInfo *rel,
+                                        Index rti, RangeTblEntry *rte);
 void set_rel_pathlist_init(void)
 {
     prev_set_rel_pathlist_hook = set_rel_pathlist_hook;
@@ -59,6 +60,7 @@ void set_rel_pathlist_fini(void)
 static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, Index rti,
                              RangeTblEntry *rte)
 {
+
     if (prev_set_rel_pathlist_hook)
         prev_set_rel_pathlist_hook(root, rel, rti, rte);
 
@@ -67,6 +69,9 @@ static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, Index rti,
     case CYPHER_CLAUSE_CREATE:
         handle_cypher_create_clause(root, rel, rti, rte);
         break;
+    case CYPHER_CLAUSE_MERGE:
+        handle_cypher_merge_clause(root, rel, rti, rte);
+        break;
     case CYPHER_CLAUSE_NONE:
         break;
     default:
@@ -103,6 +108,8 @@ static cypher_clause_kind get_cypher_clause_kind(RangeTblEntry *rte)
 
     if (is_oid_ag_func(fe->funcid, CREATE_CLAUSE_FUNCTION_NAME)) 
         return CYPHER_CLAUSE_CREATE;
+    else if (is_oid_ag_func(fe->funcid, MERGE_CLAUSE_FUNCTION_NAME))
+        return CYPHER_CLAUSE_MERGE;
     else
         return CYPHER_CLAUSE_NONE;
 }
@@ -130,3 +137,27 @@ static void handle_cypher_create_clause(PlannerInfo *root, RelOptInfo *rel,
     // Add the new path to the rel.
     add_path(rel, (Path *)cp);
 }
+
+// replace all possible paths with our CustomPath
+static void handle_cypher_merge_clause(PlannerInfo *root, RelOptInfo *rel,
+                                        Index rti, RangeTblEntry *rte)
+{
+    TargetEntry *te;
+    FuncExpr *fe;
+    List *custom_private;
+    CustomPath *cp;
+
+    // Add the pattern to the CustomPath
+    te = (TargetEntry *)llast(rte->subquery->targetList);
+    fe = (FuncExpr *)te->expr;
+    // pass the const that holds the data structure to the path.
+    custom_private = fe->args;
+
+    cp = create_cypher_merge_path(root, rel, custom_private);
+
+    // Discard any pre-existing paths
+    rel->pathlist = NIL;
+    rel->partial_pathlist = NIL;
+
+    add_path(rel, (Path *)cp);
+}