Change TRUE/FALSE to true/false

The lower case spellings are C and C++ standard and are used in most
parts of the PostgreSQL sources.  The upper case spellings are only used
in some files/modules.  So standardize on the standard spellings.

The APIs for ICU, Perl, and Windows define their own TRUE and FALSE, so
those are left as is when using those APIs.

In code comments, we use the lower-case spelling for the C concepts and
keep the upper-case spelling for the SQL concepts.

Reviewed-by: Michael Paquier <michael.paquier@gmail.com>

src/backend/optimizer/path/allpaths.c

@@ -1884,7 +1884,7 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
 	 * Zero out result area for subquery_is_pushdown_safe, so that it can set
 	 * flags as needed while recursing.  In particular, we need a workspace
 	 * for keeping track of unsafe-to-reference columns.  unsafeColumns[i]
-	 * will be set TRUE if we find that output column i of the subquery is
+	 * will be set true if we find that output column i of the subquery is
 	 * unsafe to use in a pushed-down qual.
 	 */
 	memset(&safetyInfo, 0, sizeof(safetyInfo));
@@ -2566,7 +2566,7 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
  * In addition, we make several checks on the subquery's output columns to see
  * if it is safe to reference them in pushed-down quals.  If output column k
  * is found to be unsafe to reference, we set safetyInfo->unsafeColumns[k]
- * to TRUE, but we don't reject the subquery overall since column k might not
+ * to true, but we don't reject the subquery overall since column k might not
  * be referenced by some/all quals.  The unsafeColumns[] array will be
  * consulted later by qual_is_pushdown_safe().  It's better to do it this way
  * than to make the checks directly in qual_is_pushdown_safe(), because when
@@ -2688,7 +2688,7 @@ recurse_pushdown_safe(Node *setOp, Query *topquery,
  *
  * There are several cases in which it's unsafe to push down an upper-level
  * qual if it references a particular output column of a subquery.  We check
- * each output column of the subquery and set unsafeColumns[k] to TRUE if
+ * each output column of the subquery and set unsafeColumns[k] to true if
  * that column is unsafe for a pushed-down qual to reference.  The conditions
  * checked here are:
  *

src/backend/optimizer/path/equivclass.c

@@ -72,7 +72,7 @@ static bool reconsider_full_join_clause(PlannerInfo *root,
  *	  any delay by an outer join, so its two sides can be considered equal
  *	  anywhere they are both computable; moreover that equality can be
  *	  extended transitively.  Record this knowledge in the EquivalenceClass
- *	  data structure, if applicable.  Returns TRUE if successful, FALSE if not
+ *	  data structure, if applicable.  Returns true if successful, false if not
  *	  (in which case caller should treat the clause as ordinary, not an
  *	  equivalence).
  *
@@ -602,8 +602,8 @@ add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
  * so for now we live with just reporting the first match.  See also
  * generate_implied_equalities_for_column and match_pathkeys_to_index.)
  *
- * If create_it is TRUE, we'll build a new EquivalenceClass when there is no
- * match.  If create_it is FALSE, we just return NULL when no match.
+ * If create_it is true, we'll build a new EquivalenceClass when there is no
+ * match.  If create_it is false, we just return NULL when no match.
  *
  * This can be used safely both before and after EquivalenceClass merging;
  * since it never causes merging it does not invalidate any existing ECs
@@ -1675,7 +1675,7 @@ reconsider_outer_join_clauses(PlannerInfo *root)
 /*
  * reconsider_outer_join_clauses for a single LEFT/RIGHT JOIN clause
  *
- * Returns TRUE if we were able to propagate a constant through the clause.
+ * Returns true if we were able to propagate a constant through the clause.
  */
 static bool
 reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo,
@@ -1800,7 +1800,7 @@ reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo,
 /*
  * reconsider_outer_join_clauses for a single FULL JOIN clause
  *
- * Returns TRUE if we were able to propagate a constant through the clause.
+ * Returns true if we were able to propagate a constant through the clause.
  */
 static bool
 reconsider_full_join_clause(PlannerInfo *root, RestrictInfo *rinfo)

src/backend/optimizer/path/indxpath.c

@@ -838,12 +838,12 @@ get_index_paths(PlannerInfo *root, RelOptInfo *rel,
  *
  * If skip_nonnative_saop is non-NULL, we ignore ScalarArrayOpExpr clauses
  * unless the index AM supports them directly, and we set *skip_nonnative_saop
- * to TRUE if we found any such clauses (caller must initialize the variable
- * to FALSE).  If it's NULL, we do not ignore ScalarArrayOpExpr clauses.
+ * to true if we found any such clauses (caller must initialize the variable
+ * to false).  If it's NULL, we do not ignore ScalarArrayOpExpr clauses.
  *
  * If skip_lower_saop is non-NULL, we ignore ScalarArrayOpExpr clauses for
- * non-first index columns, and we set *skip_lower_saop to TRUE if we found
- * any such clauses (caller must initialize the variable to FALSE).  If it's
+ * non-first index columns, and we set *skip_lower_saop to true if we found
+ * any such clauses (caller must initialize the variable to false).  If it's
  * NULL, we do not ignore non-first ScalarArrayOpExpr clauses, but they will
  * result in considering the scan's output to be unordered.
  *

src/backend/optimizer/path/joinpath.c

@@ -336,7 +336,7 @@ add_paths_to_joinrel(PlannerInfo *root,
  * across joins unless there's a join-order-constraint-based reason to do so.
  * So we ignore the param_source_rels restriction when this case applies.
  *
- * allow_star_schema_join() returns TRUE if the param_source_rels restriction
+ * allow_star_schema_join() returns true if the param_source_rels restriction
  * should be overridden, ie, it's okay to perform this join.
  */
 static inline bool
@@ -1880,7 +1880,7 @@ hash_inner_and_outer(PlannerInfo *root,
  *	  Select mergejoin clauses that are usable for a particular join.
  *	  Returns a list of RestrictInfo nodes for those clauses.
  *
- * *mergejoin_allowed is normally set to TRUE, but it is set to FALSE if
+ * *mergejoin_allowed is normally set to true, but it is set to false if
  * this is a right/full join and there are nonmergejoinable join clauses.
  * The executor's mergejoin machinery cannot handle such cases, so we have
  * to avoid generating a mergejoin plan.  (Note that this flag does NOT

src/backend/optimizer/path/joinrels.c

@@ -335,7 +335,7 @@ make_rels_by_clauseless_joins(PlannerInfo *root,
  *
  * On success, *sjinfo_p is set to NULL if this is to be a plain inner join,
  * else it's set to point to the associated SpecialJoinInfo node.  Also,
- * *reversed_p is set TRUE if the given relations need to be swapped to
+ * *reversed_p is set true if the given relations need to be swapped to
  * match the SpecialJoinInfo node.
  */
 static bool
@@ -1250,7 +1250,7 @@ mark_dummy_rel(RelOptInfo *rel)
  * decide there's no match for an outer row, which is pretty stupid.  So,
  * we need to detect the case.
  *
- * If only_pushed_down is TRUE, then consider only pushed-down quals.
+ * If only_pushed_down is true, then consider only pushed-down quals.
  */
 static bool
 restriction_is_constant_false(List *restrictlist, bool only_pushed_down)

src/backend/optimizer/path/pathkeys.c

@@ -162,8 +162,8 @@ pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys)
  * considered.  Otherwise child members are ignored.  (See the comments for
  * get_eclass_for_sort_expr.)
  *
- * create_it is TRUE if we should create any missing EquivalenceClass
- * needed to represent the sort key.  If it's FALSE, we return NULL if the
+ * create_it is true if we should create any missing EquivalenceClass
+ * needed to represent the sort key.  If it's false, we return NULL if the
  * sort key isn't already present in any EquivalenceClass.
  */
 static PathKey *
@@ -987,8 +987,8 @@ update_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
  *	  If successful, it returns a list of mergeclauses.
  *
  * 'pathkeys' is a pathkeys list showing the ordering of an input path.
- * 'outer_keys' is TRUE if these keys are for the outer input path,
- *			FALSE if for inner.
+ * 'outer_keys' is true if these keys are for the outer input path,
+ *			false if for inner.
  * 'restrictinfos' is a list of mergejoinable restriction clauses for the
  *			join relation being formed.
  *