Switch some allocation calls to use palloc0()

Some areas of the code used palloc() to allocate areas of memory for
structures related to the hints, and, while the fields of these
structures are initialized one by one, using palloc0() can avoid stupid
initialization mistakes.  This commit switches the most sensible
palloc() calls to palloc0().

Author: hslightdb (LightDB Enterprise Postgres)
Author: Michael Paquier

Per pull request #165, though I did not use the proposed patch.

pg_hint_plan.c

@@ -851,7 +851,7 @@ ScanMethodHintCreate(const char *hint_str, const char *keyword,
 {
 	ScanMethodHint *hint;
 
-	hint = palloc(sizeof(ScanMethodHint));
+	hint = palloc0(sizeof(ScanMethodHint));
 	hint->base.hint_str = hint_str;
 	hint->base.keyword = keyword;
 	hint->base.hint_keyword = hint_keyword;
@@ -887,7 +887,7 @@ JoinMethodHintCreate(const char *hint_str, const char *keyword,
 {
 	JoinMethodHint *hint;
 
-	hint = palloc(sizeof(JoinMethodHint));
+	hint = palloc0(sizeof(JoinMethodHint));
 	hint->base.hint_str = hint_str;
 	hint->base.keyword = keyword;
 	hint->base.hint_keyword = hint_keyword;
@@ -933,7 +933,7 @@ LeadingHintCreate(const char *hint_str, const char *keyword,
 {
 	LeadingHint	   *hint;
 
-	hint = palloc(sizeof(LeadingHint));
+	hint = palloc0(sizeof(LeadingHint));
 	hint->base.hint_str = hint_str;
 	hint->base.keyword = keyword;
 	hint->base.hint_keyword = hint_keyword;
@@ -967,7 +967,7 @@ SetHintCreate(const char *hint_str, const char *keyword,
 {
 	SetHint	   *hint;
 
-	hint = palloc(sizeof(SetHint));
+	hint = palloc0(sizeof(SetHint));
 	hint->base.hint_str = hint_str;
 	hint->base.keyword = keyword;
 	hint->base.hint_keyword = hint_keyword;
@@ -1005,7 +1005,7 @@ RowsHintCreate(const char *hint_str, const char *keyword,
 {
 	RowsHint *hint;
 
-	hint = palloc(sizeof(RowsHint));
+	hint = palloc0(sizeof(RowsHint));
 	hint->base.hint_str = hint_str;
 	hint->base.keyword = keyword;
 	hint->base.hint_keyword = hint_keyword;
@@ -1053,7 +1053,7 @@ ParallelHintCreate(const char *hint_str, const char *keyword,
 {
 	ParallelHint *hint;
 
-	hint = palloc(sizeof(ParallelHint));
+	hint = palloc0(sizeof(ParallelHint));
 	hint->base.hint_str = hint_str;
 	hint->base.keyword = keyword;
 	hint->base.hint_keyword = hint_keyword;
@@ -1104,7 +1104,7 @@ HintStateCreate(void)
 {
 	HintState   *hstate;
 
-	hstate = palloc(sizeof(HintState));
+	hstate = palloc0(sizeof(HintState));
 	hstate->hint_str = NULL;
 	hstate->nall_hints = 0;
 	hstate->max_all_hints = 0;
@@ -1659,7 +1659,7 @@ OuterInnerRelsCreate(char *name, List *outer_inner_list)
 {
 	OuterInnerRels *outer_inner;
 
-	outer_inner = palloc(sizeof(OuterInnerRels));
+	outer_inner = palloc0(sizeof(OuterInnerRels));
 	outer_inner->relation = name;
 	outer_inner->outer_inner_pair = outer_inner_list;
 
@@ -1831,7 +1831,7 @@ parse_hints(HintState *hstate, Query *parse, const char *str)
 			{
 				hstate->max_all_hints = HINT_ARRAY_DEFAULT_INITSIZE;
 				hstate->all_hints = (Hint **)
-					palloc(sizeof(Hint *) * hstate->max_all_hints);
+					palloc0(sizeof(Hint *) * hstate->max_all_hints);
 			}
 			else if (hstate->nall_hints == hstate->max_all_hints)
 			{
@@ -2189,7 +2189,7 @@ JoinMethodHintParse(JoinMethodHint *hint, const char *str)
 		 * Transform relation names from list to array to sort them with qsort
 		 * after.
 		 */
-		hint->relnames = palloc(sizeof(char *) * hint->nrels);
+		hint->relnames = palloc0(sizeof(char *) * hint->nrels);
 		foreach (l, name_list)
 		{
 			hint->relnames[i] = lfirst(l);
@@ -2387,7 +2387,7 @@ RowsHintParse(RowsHint *hint, const char *str)
 	 * Transform relation names from list to array to sort them with qsort
 	 * after.
 	 */
-	hint->relnames = palloc(sizeof(char *) * hint->nrels);
+	hint->relnames = palloc0(sizeof(char *) * hint->nrels);
 	foreach (l, name_list)
 	{
 		if (hint->nrels <= i)
@@ -3710,7 +3710,7 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
 static ParentIndexInfo *
 get_parent_index_info(Oid indexoid, Oid relid)
 {
-	ParentIndexInfo	*p_info = palloc(sizeof(ParentIndexInfo));
+	ParentIndexInfo	*p_info = palloc0(sizeof(ParentIndexInfo));
 	Relation	    indexRelation;
 	Form_pg_index	index;
 	char		   *attname;
@@ -3724,9 +3724,9 @@ get_parent_index_info(Oid indexoid, Oid relid)
 	p_info->method = indexRelation->rd_rel->relam;
 
 	p_info->column_names = NIL;
-	p_info->indcollation = (Oid *) palloc(sizeof(Oid) * index->indnatts);
-	p_info->opclass = (Oid *) palloc(sizeof(Oid) * index->indnatts);
-	p_info->indoption = (int16 *) palloc(sizeof(Oid) * index->indnatts);
+	p_info->indcollation = (Oid *) palloc0(sizeof(Oid) * index->indnatts);
+	p_info->opclass = (Oid *) palloc0(sizeof(Oid) * index->indnatts);
+	p_info->indoption = (int16 *) palloc0(sizeof(Oid) * index->indnatts);
 
 	/*
 	 * Collect relation attribute names of index columns for index