/*--------------------------------------------------------------------
 * Symbols referenced in this file:
 * - quote_identifier
 * - quote_all_identifiers
 *--------------------------------------------------------------------
 */

/*-------------------------------------------------------------------------
 *
 * ruleutils.c
 *	  Functions to convert stored expressions/querytrees back to
 *	  source text
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/utils/adt/ruleutils.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>

#include "access/amapi.h"
#include "access/htup_details.h"
#include "access/relation.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/pg_aggregate.h"
#include "catalog/pg_am.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_depend.h"
#include "catalog/pg_language.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_partitioned_table.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "commands/tablespace.h"
#include "common/keywords.h"
#include "executor/spi.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/pathnodes.h"
#include "optimizer/optimizer.h"
#include "parser/parse_agg.h"
#include "parser/parse_func.h"
#include "parser/parse_node.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parser.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "rewrite/rewriteSupport.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/guc.h"
#include "utils/hsearch.h"
#include "utils/lsyscache.h"
#include "utils/partcache.h"
#include "utils/rel.h"
#include "utils/ruleutils.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/typcache.h"
#include "utils/varlena.h"
#include "utils/xml.h"

/* ----------
 * Pretty formatting constants
 * ----------
 */

/* Indent counts */
#define PRETTYINDENT_STD		8
#define PRETTYINDENT_JOIN		4
#define PRETTYINDENT_VAR		4

#define PRETTYINDENT_LIMIT		40	/* wrap limit */

/* Pretty flags */
#define PRETTYFLAG_PAREN		0x0001
#define PRETTYFLAG_INDENT		0x0002
#define PRETTYFLAG_SCHEMA		0x0004

/* Standard conversion of a "bool pretty" option to detailed flags */
#define GET_PRETTY_FLAGS(pretty) \
	((pretty) ? (PRETTYFLAG_PAREN | PRETTYFLAG_INDENT | PRETTYFLAG_SCHEMA) \
	 : PRETTYFLAG_INDENT)

/* Default line length for pretty-print wrapping: 0 means wrap always */
#define WRAP_COLUMN_DEFAULT		0

/* macros to test if pretty action needed */
#define PRETTY_PAREN(context)	((context)->prettyFlags & PRETTYFLAG_PAREN)
#define PRETTY_INDENT(context)	((context)->prettyFlags & PRETTYFLAG_INDENT)
#define PRETTY_SCHEMA(context)	((context)->prettyFlags & PRETTYFLAG_SCHEMA)


/* ----------
 * Local data types
 * ----------
 */

/* Context info needed for invoking a recursive querytree display routine */
typedef struct
{
	StringInfo	buf;			/* output buffer to append to */
	List	   *namespaces;		/* List of deparse_namespace nodes */
	List	   *windowClause;	/* Current query level's WINDOW clause */
	List	   *windowTList;	/* targetlist for resolving WINDOW clause */
	int			prettyFlags;	/* enabling of pretty-print functions */
	int			wrapColumn;		/* max line length, or -1 for no limit */
	int			indentLevel;	/* current indent level for pretty-print */
	bool		varprefix;		/* true to print prefixes on Vars */
	ParseExprKind special_exprkind; /* set only for exprkinds needing special
									 * handling */
	Bitmapset  *appendparents;	/* if not null, map child Vars of these relids
								 * back to the parent rel */
} deparse_context;

/*
 * Each level of query context around a subtree needs a level of Var namespace.
 * A Var having varlevelsup=N refers to the N'th item (counting from 0) in
 * the current context's namespaces list.
 *
 * rtable is the list of actual RTEs from the Query or PlannedStmt.
 * rtable_names holds the alias name to be used for each RTE (either a C
 * string, or NULL for nameless RTEs such as unnamed joins).
 * rtable_columns holds the column alias names to be used for each RTE.
 *
 * subplans is a list of Plan trees for SubPlans and CTEs (it's only used
 * in the PlannedStmt case).
 * ctes is a list of CommonTableExpr nodes (only used in the Query case).
 * appendrels, if not null (it's only used in the PlannedStmt case), is an
 * array of AppendRelInfo nodes, indexed by child relid.  We use that to map
 * child-table Vars to their inheritance parents.
 *
 * In some cases we need to make names of merged JOIN USING columns unique
 * across the whole query, not only per-RTE.  If so, unique_using is true
 * and using_names is a list of C strings representing names already assigned
 * to USING columns.
 *
 * When deparsing plan trees, there is always just a single item in the
 * deparse_namespace list (since a plan tree never contains Vars with
 * varlevelsup > 0).  We store the Plan node that is the immediate
 * parent of the expression to be deparsed, as well as a list of that
 * Plan's ancestors.  In addition, we store its outer and inner subplan nodes,
 * as well as their targetlists, and the index tlist if the current plan node
 * might contain INDEX_VAR Vars.  (These fields could be derived on-the-fly
 * from the current Plan node, but it seems notationally clearer to set them
 * up as separate fields.)
 */
typedef struct
{
	List	   *rtable;			/* List of RangeTblEntry nodes */
	List	   *rtable_names;	/* Parallel list of names for RTEs */
	List	   *rtable_columns; /* Parallel list of deparse_columns structs */
	List	   *subplans;		/* List of Plan trees for SubPlans */
	List	   *ctes;			/* List of CommonTableExpr nodes */
	AppendRelInfo **appendrels; /* Array of AppendRelInfo nodes, or NULL */
	/* Workspace for column alias assignment: */
	bool		unique_using;	/* Are we making USING names globally unique */
	List	   *using_names;	/* List of assigned names for USING columns */
	/* Remaining fields are used only when deparsing a Plan tree: */
	Plan	   *plan;			/* immediate parent of current expression */
	List	   *ancestors;		/* ancestors of plan */
	Plan	   *outer_plan;		/* outer subnode, or NULL if none */
	Plan	   *inner_plan;		/* inner subnode, or NULL if none */
	List	   *outer_tlist;	/* referent for OUTER_VAR Vars */
	List	   *inner_tlist;	/* referent for INNER_VAR Vars */
	List	   *index_tlist;	/* referent for INDEX_VAR Vars */
	/* Special namespace representing a function signature: */
	char	   *funcname;
	int			numargs;
	char	  **argnames;
} deparse_namespace;

/*
 * Per-relation data about column alias names.
 *
 * Selecting aliases is unreasonably complicated because of the need to dump
 * rules/views whose underlying tables may have had columns added, deleted, or
 * renamed since the query was parsed.  We must nonetheless print the rule/view
 * in a form that can be reloaded and will produce the same results as before.
 *
 * For each RTE used in the query, we must assign column aliases that are
 * unique within that RTE.  SQL does not require this of the original query,
 * but due to factors such as *-expansion we need to be able to uniquely
 * reference every column in a decompiled query.  As long as we qualify all
 * column references, per-RTE uniqueness is sufficient for that.
 *
 * However, we can't ensure per-column name uniqueness for unnamed join RTEs,
 * since they just inherit column names from their input RTEs, and we can't
 * rename the columns at the join level.  Most of the time this isn't an issue
 * because we don't need to reference the join's output columns as such; we
 * can reference the input columns instead.  That approach can fail for merged
 * JOIN USING columns, however, so when we have one of those in an unnamed
 * join, we have to make that column's alias globally unique across the whole
 * query to ensure it can be referenced unambiguously.
 *
 * Another problem is that a JOIN USING clause requires the columns to be
 * merged to have the same aliases in both input RTEs, and that no other
 * columns in those RTEs or their children conflict with the USING names.
 * To handle that, we do USING-column alias assignment in a recursive
 * traversal of the query's jointree.  When descending through a JOIN with
 * USING, we preassign the USING column names to the child columns, overriding
 * other rules for column alias assignment.  We also mark each RTE with a list
 * of all USING column names selected for joins containing that RTE, so that
 * when we assign other columns' aliases later, we can avoid conflicts.
 *
 * Another problem is that if a JOIN's input tables have had columns added or
 * deleted since the query was parsed, we must generate a column alias list
 * for the join that matches the current set of input columns --- otherwise, a
 * change in the number of columns in the left input would throw off matching
 * of aliases to columns of the right input.  Thus, positions in the printable
 * column alias list are not necessarily one-for-one with varattnos of the
 * JOIN, so we need a separate new_colnames[] array for printing purposes.
 */
typedef struct
{
	/*
	 * colnames is an array containing column aliases to use for columns that
	 * existed when the query was parsed.  Dropped columns have NULL entries.
	 * This array can be directly indexed by varattno to get a Var's name.
	 *
	 * Non-NULL entries are guaranteed unique within the RTE, *except* when
	 * this is for an unnamed JOIN RTE.  In that case we merely copy up names
	 * from the two input RTEs.
	 *
	 * During the recursive descent in set_using_names(), forcible assignment
	 * of a child RTE's column name is represented by pre-setting that element
	 * of the child's colnames array.  So at that stage, NULL entries in this
	 * array just mean that no name has been preassigned, not necessarily that
	 * the column is dropped.
	 */
	int			num_cols;		/* length of colnames[] array */
	char	  **colnames;		/* array of C strings and NULLs */

	/*
	 * new_colnames is an array containing column aliases to use for columns
	 * that would exist if the query was re-parsed against the current
	 * definitions of its base tables.  This is what to print as the column
	 * alias list for the RTE.  This array does not include dropped columns,
	 * but it will include columns added since original parsing.  Indexes in
	 * it therefore have little to do with current varattno values.  As above,
	 * entries are unique unless this is for an unnamed JOIN RTE.  (In such an
	 * RTE, we never actually print this array, but we must compute it anyway
	 * for possible use in computing column names of upper joins.) The
	 * parallel array is_new_col marks which of these columns are new since
	 * original parsing.  Entries with is_new_col false must match the
	 * non-NULL colnames entries one-for-one.
	 */
	int			num_new_cols;	/* length of new_colnames[] array */
	char	  **new_colnames;	/* array of C strings */
	bool	   *is_new_col;		/* array of bool flags */

	/* This flag tells whether we should actually print a column alias list */
	bool		printaliases;

	/* This list has all names used as USING names in joins above this RTE */
	List	   *parentUsing;	/* names assigned to parent merged columns */

	/*
	 * If this struct is for a JOIN RTE, we fill these fields during the
	 * set_using_names() pass to describe its relationship to its child RTEs.
	 *
	 * leftattnos and rightattnos are arrays with one entry per existing
	 * output column of the join (hence, indexable by join varattno).  For a
	 * simple reference to a column of the left child, leftattnos[i] is the
	 * child RTE's attno and rightattnos[i] is zero; and conversely for a
	 * column of the right child.  But for merged columns produced by JOIN
	 * USING/NATURAL JOIN, both leftattnos[i] and rightattnos[i] are nonzero.
	 * Note that a simple reference might be to a child RTE column that's been
	 * dropped; but that's OK since the column could not be used in the query.
	 *
	 * If it's a JOIN USING, usingNames holds the alias names selected for the
	 * merged columns (these might be different from the original USING list,
	 * if we had to modify names to achieve uniqueness).
	 */
	int			leftrti;		/* rangetable index of left child */
	int			rightrti;		/* rangetable index of right child */
	int		   *leftattnos;		/* left-child varattnos of join cols, or 0 */
	int		   *rightattnos;	/* right-child varattnos of join cols, or 0 */
	List	   *usingNames;		/* names assigned to merged columns */
} deparse_columns;

/* This macro is analogous to rt_fetch(), but for deparse_columns structs */
#define deparse_columns_fetch(rangetable_index, dpns) \
	((deparse_columns *) list_nth((dpns)->rtable_columns, (rangetable_index)-1))

/*
 * Entry in set_rtable_names' hash table
 */
typedef struct
{
	char		name[NAMEDATALEN];	/* Hash key --- must be first */
	int			counter;		/* Largest addition used so far for name */
} NameHashEntry;

/* Callback signature for resolve_special_varno() */
typedef void (*rsv_callback) (Node *node, deparse_context *context,
							  void *callback_arg);


/* ----------
 * Global data
 * ----------
 */





/* GUC parameters */
__thread bool		quote_all_identifiers = false;



/* ----------
 * Local functions
 *
 * Most of these functions used to use fixed-size buffers to build their
 * results.  Now, they take an (already initialized) StringInfo object
 * as a parameter, and append their text output to its contents.
 * ----------
 */
static char *deparse_expression_pretty(Node *expr, List *dpcontext,
									   bool forceprefix, bool showimplicit,
									   int prettyFlags, int startIndent);
static char *pg_get_viewdef_worker(Oid viewoid,
								   int prettyFlags, int wrapColumn);
static char *pg_get_triggerdef_worker(Oid trigid, bool pretty);
static int	decompile_column_index_array(Datum column_index_array, Oid relId,
										 StringInfo buf);
static char *pg_get_ruledef_worker(Oid ruleoid, int prettyFlags);
static char *pg_get_indexdef_worker(Oid indexrelid, int colno,
									const Oid *excludeOps,
									bool attrsOnly, bool keysOnly,
									bool showTblSpc, bool inherits,
									int prettyFlags, bool missing_ok);
static char *pg_get_statisticsobj_worker(Oid statextid, bool columns_only,
										 bool missing_ok);
static char *pg_get_partkeydef_worker(Oid relid, int prettyFlags,
									  bool attrsOnly, bool missing_ok);
static char *pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
										 int prettyFlags, bool missing_ok);
static text *pg_get_expr_worker(text *expr, Oid relid, const char *relname,
								int prettyFlags);
static int	print_function_arguments(StringInfo buf, HeapTuple proctup,
									 bool print_table_args, bool print_defaults);
static void print_function_rettype(StringInfo buf, HeapTuple proctup);
static void print_function_trftypes(StringInfo buf, HeapTuple proctup);
static void print_function_sqlbody(StringInfo buf, HeapTuple proctup);
static void set_rtable_names(deparse_namespace *dpns, List *parent_namespaces,
							 Bitmapset *rels_used);
static void set_deparse_for_query(deparse_namespace *dpns, Query *query,
								  List *parent_namespaces);
static void set_simple_column_names(deparse_namespace *dpns);
static bool has_dangerous_join_using(deparse_namespace *dpns, Node *jtnode);
static void set_using_names(deparse_namespace *dpns, Node *jtnode,
							List *parentUsing);
static void set_relation_column_names(deparse_namespace *dpns,
									  RangeTblEntry *rte,
									  deparse_columns *colinfo);
static void set_join_column_names(deparse_namespace *dpns, RangeTblEntry *rte,
								  deparse_columns *colinfo);
static bool colname_is_unique(const char *colname, deparse_namespace *dpns,
							  deparse_columns *colinfo);
static char *make_colname_unique(char *colname, deparse_namespace *dpns,
								 deparse_columns *colinfo);
static void expand_colnames_array_to(deparse_columns *colinfo, int n);
static void identify_join_columns(JoinExpr *j, RangeTblEntry *jrte,
								  deparse_columns *colinfo);
static char *get_rtable_name(int rtindex, deparse_context *context);
static void set_deparse_plan(deparse_namespace *dpns, Plan *plan);
static Plan *find_recursive_union(deparse_namespace *dpns,
								  WorkTableScan *wtscan);
static void push_child_plan(deparse_namespace *dpns, Plan *plan,
							deparse_namespace *save_dpns);
static void pop_child_plan(deparse_namespace *dpns,
						   deparse_namespace *save_dpns);
static void push_ancestor_plan(deparse_namespace *dpns, ListCell *ancestor_cell,
							   deparse_namespace *save_dpns);
static void pop_ancestor_plan(deparse_namespace *dpns,
							  deparse_namespace *save_dpns);
static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
						 int prettyFlags);
static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
						 int prettyFlags, int wrapColumn);
static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
						  TupleDesc resultDesc, bool colNamesVisible,
						  int prettyFlags, int wrapColumn, int startIndent);
static void get_values_def(List *values_lists, deparse_context *context);
static void get_with_clause(Query *query, deparse_context *context);
static void get_select_query_def(Query *query, deparse_context *context,
								 TupleDesc resultDesc, bool colNamesVisible);
static void get_insert_query_def(Query *query, deparse_context *context,
								 bool colNamesVisible);
static void get_update_query_def(Query *query, deparse_context *context,
								 bool colNamesVisible);
static void get_update_query_targetlist_def(Query *query, List *targetList,
											deparse_context *context,
											RangeTblEntry *rte);
static void get_delete_query_def(Query *query, deparse_context *context,
								 bool colNamesVisible);
static void get_merge_query_def(Query *query, deparse_context *context,
								bool colNamesVisible);
static void get_utility_query_def(Query *query, deparse_context *context);
static void get_basic_select_query(Query *query, deparse_context *context,
								   TupleDesc resultDesc, bool colNamesVisible);
static void get_target_list(List *targetList, deparse_context *context,
							TupleDesc resultDesc, bool colNamesVisible);
static void get_setop_query(Node *setOp, Query *query,
							deparse_context *context,
							TupleDesc resultDesc, bool colNamesVisible);
static Node *get_rule_sortgroupclause(Index ref, List *tlist,
									  bool force_colno,
									  deparse_context *context);
static void get_rule_groupingset(GroupingSet *gset, List *targetlist,
								 bool omit_parens, deparse_context *context);
static void get_rule_orderby(List *orderList, List *targetList,
							 bool force_colno, deparse_context *context);
static void get_rule_windowclause(Query *query, deparse_context *context);
static void get_rule_windowspec(WindowClause *wc, List *targetList,
								deparse_context *context);
static char *get_variable(Var *var, int levelsup, bool istoplevel,
						  deparse_context *context);
static void get_special_variable(Node *node, deparse_context *context,
								 void *callback_arg);
static void resolve_special_varno(Node *node, deparse_context *context,
								  rsv_callback callback, void *callback_arg);
static Node *find_param_referent(Param *param, deparse_context *context,
								 deparse_namespace **dpns_p, ListCell **ancestor_cell_p);
static void get_parameter(Param *param, deparse_context *context);
static const char *get_simple_binary_op_name(OpExpr *expr);
static bool isSimpleNode(Node *node, Node *parentNode, int prettyFlags);
static void appendContextKeyword(deparse_context *context, const char *str,
								 int indentBefore, int indentAfter, int indentPlus);
static void removeStringInfoSpaces(StringInfo str);
static void get_rule_expr(Node *node, deparse_context *context,
						  bool showimplicit);
static void get_rule_expr_toplevel(Node *node, deparse_context *context,
								   bool showimplicit);
static void get_rule_list_toplevel(List *lst, deparse_context *context,
								   bool showimplicit);
static void get_rule_expr_funccall(Node *node, deparse_context *context,
								   bool showimplicit);
static bool looks_like_function(Node *node);
static void get_oper_expr(OpExpr *expr, deparse_context *context);
static void get_func_expr(FuncExpr *expr, deparse_context *context,
						  bool showimplicit);
static void get_agg_expr(Aggref *aggref, deparse_context *context,
						 Aggref *original_aggref);
static void get_agg_expr_helper(Aggref *aggref, deparse_context *context,
								Aggref *original_aggref, const char *funcname,
								const char *options, bool is_json_objectagg);
static void get_agg_combine_expr(Node *node, deparse_context *context,
								 void *callback_arg);
static void get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context);
static void get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
									   const char *funcname, const char *options,
									   bool is_json_objectagg);
static bool get_func_sql_syntax(FuncExpr *expr, deparse_context *context);
static void get_coercion_expr(Node *arg, deparse_context *context,
							  Oid resulttype, int32 resulttypmod,
							  Node *parentNode);
static void get_const_expr(Const *constval, deparse_context *context,
						   int showtype);
static void get_const_collation(Const *constval, deparse_context *context);
static void get_json_format(JsonFormat *format, StringInfo buf);
static void get_json_constructor(JsonConstructorExpr *ctor,
								 deparse_context *context, bool showimplicit);
static void get_json_constructor_options(JsonConstructorExpr *ctor,
										 StringInfo buf);
static void get_json_agg_constructor(JsonConstructorExpr *ctor,
									 deparse_context *context,
									 const char *funcname,
									 bool is_json_objectagg);
static void simple_quote_literal(StringInfo buf, const char *val);
static void get_sublink_expr(SubLink *sublink, deparse_context *context);
static void get_tablefunc(TableFunc *tf, deparse_context *context,
						  bool showimplicit);
static void get_from_clause(Query *query, const char *prefix,
							deparse_context *context);
static void get_from_clause_item(Node *jtnode, Query *query,
								 deparse_context *context);
static void get_rte_alias(RangeTblEntry *rte, int varno, bool use_as,
						  deparse_context *context);
static void get_column_alias_list(deparse_columns *colinfo,
								  deparse_context *context);
static void get_from_clause_coldeflist(RangeTblFunction *rtfunc,
									   deparse_columns *colinfo,
									   deparse_context *context);
static void get_tablesample_def(TableSampleClause *tablesample,
								deparse_context *context);
static void get_opclass_name(Oid opclass, Oid actual_datatype,
							 StringInfo buf);
static Node *processIndirection(Node *node, deparse_context *context);
static void printSubscripts(SubscriptingRef *sbsref, deparse_context *context);
static char *get_relation_name(Oid relid);
static char *generate_relation_name(Oid relid, List *namespaces);
static char *generate_qualified_relation_name(Oid relid);
static char *generate_function_name(Oid funcid, int nargs,
									List *argnames, Oid *argtypes,
									bool has_variadic, bool *use_variadic_p,
									ParseExprKind special_exprkind);
static char *generate_operator_name(Oid operid, Oid arg1, Oid arg2);
static void add_cast_to(StringInfo buf, Oid typid);
static char *generate_qualified_type_name(Oid typid);
static text *string_to_text(char *str);
static char *flatten_reloptions(Oid relid);
static void get_reloptions(StringInfo buf, Datum reloptions);

#define only_marker(rte)  ((rte)->inh ? "" : "ONLY ")


/* ----------
 * pg_get_ruledef		- Do it all and return a text
 *				  that could be used as a statement
 *				  to recreate the rule
 * ----------
 */









/* ----------
 * pg_get_viewdef		- Mainly the same thing, but we
 *				  only return the SELECT part of a view
 * ----------
 */












/*
 * Common code for by-OID and by-name variants of pg_get_viewdef
 */


/* ----------
 * pg_get_triggerdef		- Get the definition of a trigger
 * ----------
 */






/* ----------
 * pg_get_indexdef			- Get the definition of an index
 *
 * In the extended version, there is a colno argument as well as pretty bool.
 *	if colno == 0, we want a complete index definition.
 *	if colno > 0, we only want the Nth index key's variable or expression.
 *
 * Note that the SQL-function versions of this omit any info about the
 * index tablespace; this is intentional because pg_dump wants it that way.
 * However pg_get_indexdef_string() includes the index tablespace.
 * ----------
 */




/*
 * Internal version for use by ALTER TABLE.
 * Includes a tablespace clause in the result.
 * Returns a palloc'd C string; no pretty-printing.
 */


/* Internal version that just reports the key-column definitions */


/* Internal version, extensible with flags to control its behavior */


/*
 * Internal workhorse to decompile an index definition.
 *
 * This is now used for exclusion constraints as well: if excludeOps is not
 * NULL then it points to an array of exclusion operator OIDs.
 */


/* ----------
 * pg_get_querydef
 *
 * Public entry point to deparse one query parsetree.
 * The pretty flags are determined by GET_PRETTY_FLAGS(pretty).
 *
 * The result is a palloc'd C string.
 * ----------
 */


/*
 * pg_get_statisticsobjdef
 *		Get the definition of an extended statistics object
 */


/*
 * Internal version for use by ALTER TABLE.
 * Includes a tablespace clause in the result.
 * Returns a palloc'd C string; no pretty-printing.
 */


/*
 * pg_get_statisticsobjdef_columns
 *		Get columns and expressions for an extended statistics object
 */


/*
 * Internal workhorse to decompile an extended statistics object.
 */


/*
 * Generate text array of expressions for statistics object.
 */


/*
 * pg_get_partkeydef
 *
 * Returns the partition key specification, ie, the following:
 *
 * { RANGE | LIST | HASH } (column opt_collation opt_opclass [, ...])
 */


/* Internal version that just reports the column definitions */


/*
 * Internal workhorse to decompile a partition key definition.
 */


/*
 * pg_get_partition_constraintdef
 *
 * Returns partition constraint expression as a string for the input relation
 */


/*
 * pg_get_partconstrdef_string
 *
 * Returns the partition constraint as a C-string for the input relation, with
 * the given alias.  No pretty-printing.
 */


/*
 * pg_get_constraintdef
 *
 * Returns the definition for the constraint, ie, everything that needs to
 * appear after "ALTER TABLE ... ADD CONSTRAINT <constraintname>".
 */




/*
 * Internal version that returns a full ALTER TABLE ... ADD CONSTRAINT command
 */


/*
 * As of 9.4, we now use an MVCC snapshot for this.
 */



/*
 * Convert an int16[] Datum into a comma-separated list of column names
 * for the indicated relation; append the list to buf.  Returns the number
 * of keys.
 */



/* ----------
 * pg_get_expr			- Decompile an expression tree
 *
 * Input: an expression tree in nodeToString form, and a relation OID
 *
 * Output: reverse-listed expression
 *
 * Currently, the expression can only refer to a single relation, namely
 * the one specified by the second parameter.  This is sufficient for
 * partial indexes, column default expressions, etc.  We also support
 * Var-free expressions, for which the OID can be InvalidOid.
 *
 * We expect this function to work, or throw a reasonably clean error,
 * for any node tree that can appear in a catalog pg_node_tree column.
 * Query trees, such as those appearing in pg_rewrite.ev_action, are
 * not supported.  Nor are expressions in more than one relation, which
 * can appear in places like pg_rewrite.ev_qual.
 * ----------
 */







/* ----------
 * pg_get_userbyid		- Get a user name by roleid and
 *				  fallback to 'unknown (OID=n)'
 * ----------
 */



/*
 * pg_get_serial_sequence
 *		Get the name of the sequence used by an identity or serial column,
 *		formatted suitably for passing to setval, nextval or currval.
 *		First parameter is not treated as double-quoted, second parameter
 *		is --- see documentation for reason.
 */



/*
 * pg_get_functiondef
 *		Returns the complete "CREATE OR REPLACE FUNCTION ..." statement for
 *		the specified function.
 *
 * Note: if you change the output format of this function, be careful not
 * to break psql's rules (in \ef and \sf) for identifying the start of the
 * function body.  To wit: the function body starts on a line that begins with
 * "AS ", "BEGIN ", or "RETURN ", and no preceding line will look like that.
 */


/*
 * pg_get_function_arguments
 *		Get a nicely-formatted list of arguments for a function.
 *		This is everything that would go between the parentheses in
 *		CREATE FUNCTION.
 */


/*
 * pg_get_function_identity_arguments
 *		Get a formatted list of arguments for a function.
 *		This is everything that would go between the parentheses in
 *		ALTER FUNCTION, etc.  In particular, don't print defaults.
 */


/*
 * pg_get_function_result
 *		Get a nicely-formatted version of the result type of a function.
 *		This is what would appear after RETURNS in CREATE FUNCTION.
 */


/*
 * Guts of pg_get_function_result: append the function's return type
 * to the specified buffer.
 */


/*
 * Common code for pg_get_function_arguments and pg_get_function_result:
 * append the desired subset of arguments to buf.  We print only TABLE
 * arguments when print_table_args is true, and all the others when it's false.
 * We print argument defaults only if print_defaults is true.
 * Function return value is the number of arguments printed.
 */




/*
 * Append used transformed types to specified buffer
 */


/*
 * Get textual representation of a function argument's default value.  The
 * second argument of this function is the argument number among all arguments
 * (i.e. proallargtypes, *not* proargtypes), starting with 1, because that's
 * how information_schema.sql uses it.
 */







/*
 * deparse_expression			- General utility for deparsing expressions
 *
 * calls deparse_expression_pretty with all prettyPrinting disabled
 */


/* ----------
 * deparse_expression_pretty	- General utility for deparsing expressions
 *
 * expr is the node tree to be deparsed.  It must be a transformed expression
 * tree (ie, not the raw output of gram.y).
 *
 * dpcontext is a list of deparse_namespace nodes representing the context
 * for interpreting Vars in the node tree.  It can be NIL if no Vars are
 * expected.
 *
 * forceprefix is true to force all Vars to be prefixed with their table names.
 *
 * showimplicit is true to force all implicit casts to be shown explicitly.
 *
 * Tries to pretty up the output according to prettyFlags and startIndent.
 *
 * The result is a palloc'd string.
 * ----------
 */


/* ----------
 * deparse_context_for			- Build deparse context for a single relation
 *
 * Given the reference name (alias) and OID of a relation, build deparsing
 * context for an expression referencing only that relation (as varno 1,
 * varlevelsup 0).  This is sufficient for many uses of deparse_expression.
 * ----------
 */


/*
 * deparse_context_for_plan_tree - Build deparse context for a Plan tree
 *
 * When deparsing an expression in a Plan tree, we use the plan's rangetable
 * to resolve names of simple Vars.  The initialization of column names for
 * this is rather expensive if the rangetable is large, and it'll be the same
 * for every expression in the Plan tree; so we do it just once and re-use
 * the result of this function for each expression.  (Note that the result
 * is not usable until set_deparse_context_plan() is applied to it.)
 *
 * In addition to the PlannedStmt, pass the per-RTE alias names
 * assigned by a previous call to select_rtable_names_for_explain.
 */


/*
 * set_deparse_context_plan - Specify Plan node containing expression
 *
 * When deparsing an expression in a Plan tree, we might have to resolve
 * OUTER_VAR, INNER_VAR, or INDEX_VAR references.  To do this, the caller must
 * provide the parent Plan node.  Then OUTER_VAR and INNER_VAR references
 * can be resolved by drilling down into the left and right child plans.
 * Similarly, INDEX_VAR references can be resolved by reference to the
 * indextlist given in a parent IndexOnlyScan node, or to the scan tlist in
 * ForeignScan and CustomScan nodes.  (Note that we don't currently support
 * deparsing of indexquals in regular IndexScan or BitmapIndexScan nodes;
 * for those, we can only deparse the indexqualorig fields, which won't
 * contain INDEX_VAR Vars.)
 *
 * The ancestors list is a list of the Plan's parent Plan and SubPlan nodes,
 * the most-closely-nested first.  This is needed to resolve PARAM_EXEC
 * Params.  Note we assume that all the Plan nodes share the same rtable.
 *
 * Once this function has been called, deparse_expression() can be called on
 * subsidiary expression(s) of the specified Plan node.  To deparse
 * expressions of a different Plan node in the same Plan tree, re-call this
 * function to identify the new parent Plan node.
 *
 * The result is the same List passed in; this is a notational convenience.
 */


/*
 * select_rtable_names_for_explain	- Select RTE aliases for EXPLAIN
 *
 * Determine the relation aliases we'll use during an EXPLAIN operation.
 * This is just a frontend to set_rtable_names.  We have to expose the aliases
 * to EXPLAIN because EXPLAIN needs to know the right alias names to print.
 */


/*
 * set_rtable_names: select RTE aliases to be used in printing a query
 *
 * We fill in dpns->rtable_names with a list of names that is one-for-one with
 * the already-filled dpns->rtable list.  Each RTE name is unique among those
 * in the new namespace plus any ancestor namespaces listed in
 * parent_namespaces.
 *
 * If rels_used isn't NULL, only RTE indexes listed in it are given aliases.
 *
 * Note that this function is only concerned with relation names, not column
 * names.
 */


/*
 * set_deparse_for_query: set up deparse_namespace for deparsing a Query tree
 *
 * For convenience, this is defined to initialize the deparse_namespace struct
 * from scratch.
 */


/*
 * set_simple_column_names: fill in column aliases for non-query situations
 *
 * This handles EXPLAIN and cases where we only have relation RTEs.  Without
 * a join tree, we can't do anything smart about join RTEs, but we don't
 * need to (note that EXPLAIN should never see join alias Vars anyway).
 * If we do hit a join RTE we'll just process it like a non-table base RTE.
 */


/*
 * has_dangerous_join_using: search jointree for unnamed JOIN USING
 *
 * Merged columns of a JOIN USING may act differently from either of the input
 * columns, either because they are merged with COALESCE (in a FULL JOIN) or
 * because an implicit coercion of the underlying input column is required.
 * In such a case the column must be referenced as a column of the JOIN not as
 * a column of either input.  And this is problematic if the join is unnamed
 * (alias-less): we cannot qualify the column's name with an RTE name, since
 * there is none.  (Forcibly assigning an alias to the join is not a solution,
 * since that will prevent legal references to tables below the join.)
 * To ensure that every column in the query is unambiguously referenceable,
 * we must assign such merged columns names that are globally unique across
 * the whole query, aliasing other columns out of the way as necessary.
 *
 * Because the ensuing re-aliasing is fairly damaging to the readability of
 * the query, we don't do this unless we have to.  So, we must pre-scan
 * the join tree to see if we have to, before starting set_using_names().
 */


/*
 * set_using_names: select column aliases to be used for merged USING columns
 *
 * We do this during a recursive descent of the query jointree.
 * dpns->unique_using must already be set to determine the global strategy.
 *
 * Column alias info is saved in the dpns->rtable_columns list, which is
 * assumed to be filled with pre-zeroed deparse_columns structs.
 *
 * parentUsing is a list of all USING aliases assigned in parent joins of
 * the current jointree node.  (The passed-in list must not be modified.)
 */


/*
 * set_relation_column_names: select column aliases for a non-join RTE
 *
 * Column alias info is saved in *colinfo, which is assumed to be pre-zeroed.
 * If any colnames entries are already filled in, those override local
 * choices.
 */


/*
 * set_join_column_names: select column aliases for a join RTE
 *
 * Column alias info is saved in *colinfo, which is assumed to be pre-zeroed.
 * If any colnames entries are already filled in, those override local
 * choices.  Also, names for USING columns were already chosen by
 * set_using_names().  We further expect that column alias selection has been
 * completed for both input RTEs.
 */
#ifdef USE_ASSERT_CHECKING
#endif

/*
 * colname_is_unique: is colname distinct from already-chosen column names?
 *
 * dpns is query-wide info, colinfo is for the column's RTE
 */


/*
 * make_colname_unique: modify colname if necessary to make it unique
 *
 * dpns is query-wide info, colinfo is for the column's RTE
 */


/*
 * expand_colnames_array_to: make colinfo->colnames at least n items long
 *
 * Any added array entries are initialized to zero.
 */


/*
 * identify_join_columns: figure out where columns of a join come from
 *
 * Fills the join-specific fields of the colinfo struct, except for
 * usingNames which is filled later.
 */


/*
 * get_rtable_name: convenience function to get a previously assigned RTE alias
 *
 * The RTE must belong to the topmost namespace level in "context".
 */


/*
 * set_deparse_plan: set up deparse_namespace to parse subexpressions
 * of a given Plan node
 *
 * This sets the plan, outer_plan, inner_plan, outer_tlist, inner_tlist,
 * and index_tlist fields.  Caller must already have adjusted the ancestors
 * list if necessary.  Note that the rtable, subplans, and ctes fields do
 * not need to change when shifting attention to different plan nodes in a
 * single plan tree.
 */


/*
 * Locate the ancestor plan node that is the RecursiveUnion generating
 * the WorkTableScan's work table.  We can match on wtParam, since that
 * should be unique within the plan tree.
 */


/*
 * push_child_plan: temporarily transfer deparsing attention to a child plan
 *
 * When expanding an OUTER_VAR or INNER_VAR reference, we must adjust the
 * deparse context in case the referenced expression itself uses
 * OUTER_VAR/INNER_VAR.  We modify the top stack entry in-place to avoid
 * affecting levelsup issues (although in a Plan tree there really shouldn't
 * be any).
 *
 * Caller must provide a local deparse_namespace variable to save the
 * previous state for pop_child_plan.
 */


/*
 * pop_child_plan: undo the effects of push_child_plan
 */


/*
 * push_ancestor_plan: temporarily transfer deparsing attention to an
 * ancestor plan
 *
 * When expanding a Param reference, we must adjust the deparse context
 * to match the plan node that contains the expression being printed;
 * otherwise we'd fail if that expression itself contains a Param or
 * OUTER_VAR/INNER_VAR/INDEX_VAR variable.
 *
 * The target ancestor is conveniently identified by the ListCell holding it
 * in dpns->ancestors.
 *
 * Caller must provide a local deparse_namespace variable to save the
 * previous state for pop_ancestor_plan.
 */


/*
 * pop_ancestor_plan: undo the effects of push_ancestor_plan
 */



/* ----------
 * make_ruledef			- reconstruct the CREATE RULE command
 *				  for a given pg_rewrite tuple
 * ----------
 */



/* ----------
 * make_viewdef			- reconstruct the SELECT part of a
 *				  view rewrite rule
 * ----------
 */



/* ----------
 * get_query_def			- Parse back one query parsetree
 *
 * query: parsetree to be displayed
 * buf: output text is appended to buf
 * parentnamespace: list (initially empty) of outer-level deparse_namespace's
 * resultDesc: if not NULL, the output tuple descriptor for the view
 *		represented by a SELECT query.  We use the column names from it
 *		to label SELECT output columns, in preference to names in the query
 * colNamesVisible: true if the surrounding context cares about the output
 *		column names at all (as, for example, an EXISTS() context does not);
 *		when false, we can suppress dummy column labels such as "?column?"
 * prettyFlags: bitmask of PRETTYFLAG_XXX options
 * wrapColumn: maximum line length, or -1 to disable wrapping
 * startIndent: initial indentation amount
 * ----------
 */


/* ----------
 * get_values_def			- Parse back a VALUES list
 * ----------
 */


/* ----------
 * get_with_clause			- Parse back a WITH clause
 * ----------
 */


/* ----------
 * get_select_query_def			- Parse back a SELECT parsetree
 * ----------
 */


/*
 * Detect whether query looks like SELECT ... FROM VALUES(),
 * with no need to rename the output columns of the VALUES RTE.
 * If so, return the VALUES RTE.  Otherwise return NULL.
 */




/* ----------
 * get_target_list			- Parse back a SELECT target list
 *
 * This is also used for RETURNING lists in INSERT/UPDATE/DELETE.
 *
 * resultDesc and colNamesVisible are as for get_query_def()
 * ----------
 */




/*
 * Display a sort/group clause.
 *
 * Also returns the expression tree, so caller need not find it again.
 */


/*
 * Display a GroupingSet
 */


/*
 * Display an ORDER BY list.
 */


/*
 * Display a WINDOW clause.
 *
 * Note that the windowClause list might contain only anonymous window
 * specifications, in which case we should print nothing here.
 */


/*
 * Display a window definition
 */


/* ----------
 * get_insert_query_def			- Parse back an INSERT parsetree
 * ----------
 */



/* ----------
 * get_update_query_def			- Parse back an UPDATE parsetree
 * ----------
 */



/* ----------
 * get_update_query_targetlist_def			- Parse back an UPDATE targetlist
 * ----------
 */



/* ----------
 * get_delete_query_def			- Parse back a DELETE parsetree
 * ----------
 */



/* ----------
 * get_merge_query_def				- Parse back a MERGE parsetree
 * ----------
 */



/* ----------
 * get_utility_query_def			- Parse back a UTILITY parsetree
 * ----------
 */


/*
 * Display a Var appropriately.
 *
 * In some cases (currently only when recursing into an unnamed join)
 * the Var's varlevelsup has to be interpreted with respect to a context
 * above the current one; levelsup indicates the offset.
 *
 * If istoplevel is true, the Var is at the top level of a SELECT's
 * targetlist, which means we need special treatment of whole-row Vars.
 * Instead of the normal "tab.*", we'll print "tab.*::typename", which is a
 * dirty hack to prevent "tab.*" from being expanded into multiple columns.
 * (The parser will strip the useless coercion, so no inefficiency is added in
 * dump and reload.)  We used to print just "tab" in such cases, but that is
 * ambiguous and will yield the wrong result if "tab" is also a plain column
 * name in the query.
 *
 * Returns the attname of the Var, or NULL if the Var has no attname (because
 * it is a whole-row Var or a subplan output reference).
 */


/*
 * Deparse a Var which references OUTER_VAR, INNER_VAR, or INDEX_VAR.  This
 * routine is actually a callback for resolve_special_varno, which handles
 * finding the correct TargetEntry.  We get the expression contained in that
 * TargetEntry and just need to deparse it, a job we can throw back on
 * get_rule_expr.
 */


/*
 * Chase through plan references to special varnos (OUTER_VAR, INNER_VAR,
 * INDEX_VAR) until we find a real Var or some kind of non-Var node; then,
 * invoke the callback provided.
 */


/*
 * Get the name of a field of an expression of composite type.  The
 * expression is usually a Var, but we handle other cases too.
 *
 * levelsup is an extra offset to interpret the Var's varlevelsup correctly.
 *
 * This is fairly straightforward when the expression has a named composite
 * type; we need only look up the type in the catalogs.  However, the type
 * could also be RECORD.  Since no actual table or view column is allowed to
 * have type RECORD, a Var of type RECORD must refer to a JOIN or FUNCTION RTE
 * or to a subquery output.  We drill down to find the ultimate defining
 * expression and attempt to infer the field name from it.  We ereport if we
 * can't determine the name.
 *
 * Similarly, a PARAM of type RECORD has to refer to some expression of
 * a determinable composite type.
 */


/*
 * Try to find the referenced expression for a PARAM_EXEC Param that might
 * reference a parameter supplied by an upper NestLoop or SubPlan plan node.
 *
 * If successful, return the expression and set *dpns_p and *ancestor_cell_p
 * appropriately for calling push_ancestor_plan().  If no referent can be
 * found, return NULL.
 */


/*
 * Display a Param appropriately.
 */


/*
 * get_simple_binary_op_name
 *
 * helper function for isSimpleNode
 * will return single char binary operator name, or NULL if it's not
 */



/*
 * isSimpleNode - check if given node is simple (doesn't need parenthesizing)
 *
 *	true   : simple in the context of parent node's type
 *	false  : not simple
 */



/*
 * appendContextKeyword - append a keyword to buffer
 *
 * If prettyPrint is enabled, perform a line break, and adjust indentation.
 * Otherwise, just append the keyword.
 */


/*
 * removeStringInfoSpaces - delete trailing spaces from a buffer.
 *
 * Possibly this should move to stringinfo.c at some point.
 */



/*
 * get_rule_expr_paren	- deparse expr using get_rule_expr,
 * embracing the string with parentheses if necessary for prettyPrint.
 *
 * Never embrace if prettyFlags=0, because it's done in the calling node.
 *
 * Any node that does *not* embrace its argument node by sql syntax (with
 * parentheses, non-operator keywords like CASE/WHEN/ON, or comma etc) should
 * use get_rule_expr_paren instead of get_rule_expr so parentheses can be
 * added.
 */



/* ----------
 * get_rule_expr			- Parse back an expression
 *
 * Note: showimplicit determines whether we display any implicit cast that
 * is present at the top of the expression tree.  It is a passed argument,
 * not a field of the context struct, because we change the value as we
 * recurse down into the expression.  In general we suppress implicit casts
 * when the result type is known with certainty (eg, the arguments of an
 * OR must be boolean).  We display implicit casts for arguments of functions
 * and operators, since this is needed to be certain that the same function
 * or operator will be chosen when the expression is re-parsed.
 * ----------
 */


/*
 * get_rule_expr_toplevel		- Parse back a toplevel expression
 *
 * Same as get_rule_expr(), except that if the expr is just a Var, we pass
 * istoplevel = true not false to get_variable().  This causes whole-row Vars
 * to get printed with decoration that will prevent expansion of "*".
 * We need to use this in contexts such as ROW() and VALUES(), where the
 * parser would expand "foo.*" appearing at top level.  (In principle we'd
 * use this in get_target_list() too, but that has additional worries about
 * whether to print AS, so it needs to invoke get_variable() directly anyway.)
 */


/*
 * get_rule_list_toplevel		- Parse back a list of toplevel expressions
 *
 * Apply get_rule_expr_toplevel() to each element of a List.
 *
 * This adds commas between the expressions, but caller is responsible
 * for printing surrounding decoration.
 */


/*
 * get_rule_expr_funccall		- Parse back a function-call expression
 *
 * Same as get_rule_expr(), except that we guarantee that the output will
 * look like a function call, or like one of the things the grammar treats as
 * equivalent to a function call (see the func_expr_windowless production).
 * This is needed in places where the grammar uses func_expr_windowless and
 * you can't substitute a parenthesized a_expr.  If what we have isn't going
 * to look like a function call, wrap it in a dummy CAST() expression, which
 * will satisfy the grammar --- and, indeed, is likely what the user wrote to
 * produce such a thing.
 */


/*
 * Helper function to identify node types that satisfy func_expr_windowless.
 * If in doubt, "false" is always a safe answer.
 */



/*
 * get_oper_expr			- Parse back an OpExpr node
 */


/*
 * get_func_expr			- Parse back a FuncExpr node
 */


/*
 * get_agg_expr			- Parse back an Aggref node
 */


/*
 * get_agg_expr_helper		- subroutine for get_agg_expr and
 *							get_json_agg_constructor
 */


/*
 * This is a helper function for get_agg_expr().  It's used when we deparse
 * a combining Aggref; resolve_special_varno locates the corresponding partial
 * Aggref and then calls this.
 */


/*
 * get_windowfunc_expr	- Parse back a WindowFunc node
 */



/*
 * get_windowfunc_expr_helper	- subroutine for get_windowfunc_expr and
 *								get_json_agg_constructor
 */


/*
 * get_func_sql_syntax		- Parse back a SQL-syntax function call
 *
 * Returns true if we successfully deparsed, false if we did not
 * recognize the function.
 */


/* ----------
 * get_coercion_expr
 *
 *	Make a string representation of a value coerced to a specific type
 * ----------
 */


/* ----------
 * get_const_expr
 *
 *	Make a string representation of a Const
 *
 * showtype can be -1 to never show "::typename" decoration, or +1 to always
 * show it, or 0 to show it only if the constant wouldn't be assumed to be
 * the right type by default.
 *
 * If the Const's collation isn't default for its type, show that too.
 * We mustn't do this when showtype is -1 (since that means the caller will
 * print "::typename", and we can't put a COLLATE clause in between).  It's
 * caller's responsibility that collation isn't missed in such cases.
 * ----------
 */


/*
 * helper for get_const_expr: append COLLATE if needed
 */


/*
 * get_json_format			- Parse back a JsonFormat node
 */


/*
 * get_json_returning		- Parse back a JsonReturning structure
 */


/*
 * get_json_constructor		- Parse back a JsonConstructorExpr node
 */


/*
 * Append options, if any, to the JSON constructor being deparsed
 */


/*
 * get_json_agg_constructor - Parse back an aggregate JsonConstructorExpr node
 */


/*
 * simple_quote_literal - Format a string as a SQL literal, append to buf
 */



/* ----------
 * get_sublink_expr			- Parse back a sublink
 * ----------
 */



/* ----------
 * get_tablefunc			- Parse back a table function
 * ----------
 */


/* ----------
 * get_from_clause			- Parse back a FROM clause
 *
 * "prefix" is the keyword that denotes the start of the list of FROM
 * elements. It is FROM when used to parse back SELECT and UPDATE, but
 * is USING when parsing back DELETE.
 * ----------
 */




/*
 * get_rte_alias - print the relation's alias, if needed
 *
 * If printed, the alias is preceded by a space, or by " AS " if use_as is true.
 */


/*
 * get_column_alias_list - print column alias list for an RTE
 *
 * Caller must already have printed the relation's alias name.
 */


/*
 * get_from_clause_coldeflist - reproduce FROM clause coldeflist
 *
 * When printing a top-level coldeflist (which is syntactically also the
 * relation's column alias list), use column names from colinfo.  But when
 * printing a coldeflist embedded inside ROWS FROM(), we prefer to use the
 * original coldeflist's names, which are available in rtfunc->funccolnames.
 * Pass NULL for colinfo to select the latter behavior.
 *
 * The coldeflist is appended immediately (no space) to buf.  Caller is
 * responsible for ensuring that an alias or AS is present before it.
 */


/*
 * get_tablesample_def			- print a TableSampleClause
 */


/*
 * get_opclass_name			- fetch name of an index operator class
 *
 * The opclass name is appended (after a space) to buf.
 *
 * Output is suppressed if the opclass is the default for the given
 * actual_datatype.  (If you don't want this behavior, just pass
 * InvalidOid for actual_datatype.)
 */


/*
 * generate_opclass_name
 *		Compute the name to display for an opclass specified by OID
 *
 * The result includes all necessary quoting and schema-prefixing.
 */


/*
 * processIndirection - take care of array and subfield assignment
 *
 * We strip any top-level FieldStore or assignment SubscriptingRef nodes that
 * appear in the input, printing them as decoration for the base column
 * name (which we assume the caller just printed).  We might also need to
 * strip CoerceToDomain nodes, but only ones that appear above assignment
 * nodes.
 *
 * Returns the subexpression that's to be assigned.
 */




/*
 * quote_identifier			- Quote an identifier only if needed
 *
 * When quotes are needed, we palloc the required space; slightly
 * space-wasteful but well worth it for notational simplicity.
 */
const char *
quote_identifier(const char *ident)
{
	/*
	 * Can avoid quoting if ident starts with a lowercase letter or underscore
	 * and contains only lowercase letters, digits, and underscores, *and* is
	 * not any SQL keyword.  Otherwise, supply quotes.
	 */
	int			nquotes = 0;
	bool		safe;
	const char *ptr;
	char	   *result;
	char	   *optr;

	/*
	 * would like to use <ctype.h> macros here, but they might yield unwanted
	 * locale-specific results...
	 */
	safe = ((ident[0] >= 'a' && ident[0] <= 'z') || ident[0] == '_');

	for (ptr = ident; *ptr; ptr++)
	{
		char		ch = *ptr;

		if ((ch >= 'a' && ch <= 'z') ||
			(ch >= '0' && ch <= '9') ||
			(ch == '_'))
		{
			/* okay */
		}
		else
		{
			safe = false;
			if (ch == '"')
				nquotes++;
		}
	}

	if (quote_all_identifiers)
		safe = false;

	if (safe)
	{
		/*
		 * Check for keyword.  We quote keywords except for unreserved ones.
		 * (In some cases we could avoid quoting a col_name or type_func_name
		 * keyword, but it seems much harder than it's worth to tell that.)
		 *
		 * Note: ScanKeywordLookup() does case-insensitive comparison, but
		 * that's fine, since we already know we have all-lower-case.
		 */
		int			kwnum = ScanKeywordLookup(ident, &ScanKeywords);

		if (kwnum >= 0 && ScanKeywordCategories[kwnum] != UNRESERVED_KEYWORD)
			safe = false;
	}

	if (safe)
		return ident;			/* no change needed */

	result = (char *) palloc(strlen(ident) + nquotes + 2 + 1);

	optr = result;
	*optr++ = '"';
	for (ptr = ident; *ptr; ptr++)
	{
		char		ch = *ptr;

		if (ch == '"')
			*optr++ = '"';
		*optr++ = ch;
	}
	*optr++ = '"';
	*optr = '\0';

	return result;
}

/*
 * quote_qualified_identifier	- Quote a possibly-qualified identifier
 *
 * Return a name of the form qualifier.ident, or just ident if qualifier
 * is NULL, quoting each component if necessary.  The result is palloc'd.
 */


/*
 * get_relation_name
 *		Get the unqualified name of a relation specified by OID
 *
 * This differs from the underlying get_rel_name() function in that it will
 * throw error instead of silently returning NULL if the OID is bad.
 */


/*
 * generate_relation_name
 *		Compute the name to display for a relation specified by OID
 *
 * The result includes all necessary quoting and schema-prefixing.
 *
 * If namespaces isn't NIL, it must be a list of deparse_namespace nodes.
 * We will forcibly qualify the relation name if it equals any CTE name
 * visible in the namespace list.
 */


/*
 * generate_qualified_relation_name
 *		Compute the name to display for a relation specified by OID
 *
 * As above, but unconditionally schema-qualify the name.
 */


/*
 * generate_function_name
 *		Compute the name to display for a function specified by OID,
 *		given that it is being called with the specified actual arg names and
 *		types.  (Those matter because of ambiguous-function resolution rules.)
 *
 * If we're dealing with a potentially variadic function (in practice, this
 * means a FuncExpr or Aggref, not some other way of calling a function), then
 * has_variadic must specify whether variadic arguments have been merged,
 * and *use_variadic_p will be set to indicate whether to print VARIADIC in
 * the output.  For non-FuncExpr cases, has_variadic should be false and
 * use_variadic_p can be NULL.
 *
 * The result includes all necessary quoting and schema-prefixing.
 */


/*
 * generate_operator_name
 *		Compute the name to display for an operator specified by OID,
 *		given that it is being called with the specified actual arg types.
 *		(Arg types matter because of ambiguous-operator resolution rules.
 *		Pass InvalidOid for unused arg of a unary operator.)
 *
 * The result includes all necessary quoting and schema-prefixing,
 * plus the OPERATOR() decoration needed to use a qualified operator name
 * in an expression.
 */


/*
 * generate_operator_clause --- generate a binary-operator WHERE clause
 *
 * This is used for internally-generated-and-executed SQL queries, where
 * precision is essential and readability is secondary.  The basic
 * requirement is to append "leftop op rightop" to buf, where leftop and
 * rightop are given as strings and are assumed to yield types leftoptype
 * and rightoptype; the operator is identified by OID.  The complexity
 * comes from needing to be sure that the parser will select the desired
 * operator when the query is parsed.  We always name the operator using
 * OPERATOR(schema.op) syntax, so as to avoid search-path uncertainties.
 * We have to emit casts too, if either input isn't already the input type
 * of the operator; else we are at the mercy of the parser's heuristics for
 * ambiguous-operator resolution.  The caller must ensure that leftop and
 * rightop are suitable arguments for a cast operation; it's best to insert
 * parentheses if they aren't just variables or parameters.
 */


/*
 * Add a cast specification to buf.  We spell out the type name the hard way,
 * intentionally not using format_type_be().  This is to avoid corner cases
 * for CHARACTER, BIT, and perhaps other types, where specifying the type
 * using SQL-standard syntax results in undesirable data truncation.  By
 * doing it this way we can be certain that the cast will have default (-1)
 * target typmod.
 */


/*
 * generate_qualified_type_name
 *		Compute the name to display for a type specified by OID
 *
 * This is different from format_type_be() in that we unconditionally
 * schema-qualify the name.  That also means no special syntax for
 * SQL-standard type names ... although in current usage, this should
 * only get used for domains, so such cases wouldn't occur anyway.
 */


/*
 * generate_collation_name
 *		Compute the name to display for a collation specified by OID
 *
 * The result includes all necessary quoting and schema-prefixing.
 */


/*
 * Given a C string, produce a TEXT datum.
 *
 * We assume that the input was palloc'd and may be freed.
 */


/*
 * Generate a C string representing a relation options from text[] datum.
 */


/*
 * Generate a C string representing a relation's reloptions, or NULL if none.
 */


/*
 * get_range_partbound_string
 *		A C string representation of one range partition bound
 */