pl_comp.c

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/*-------------------------------------------------------------------------
 *
 * pl_comp.c		- Compiler part of the PL/pgSQL
 *			  procedural language
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_comp.c,v 1.121 2008/01/01 19:46:00 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "plpgsql.h"

#include <ctype.h>

#include "pl.tab.h"

#include "access/heapam.h"
#include "catalog/namespace.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_attribute.h"
#include "catalog/pg_class.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "nodes/makefuncs.h"
#include "parser/gramparse.h"
#include "parser/parse_type.h"
#include "tcop/tcopprot.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/syscache.h"


/* ----------
 * Our own local and global variables
 * ----------
 */
static int	datums_alloc;
int			plpgsql_nDatums;
PLpgSQL_datum **plpgsql_Datums;
static int	datums_last = 0;

int			plpgsql_error_lineno;
char	   *plpgsql_error_funcname;
bool		plpgsql_DumpExecTree = false;
bool		plpgsql_check_syntax = false;

PLpgSQL_function *plpgsql_curr_compile;

/* A context appropriate for short-term allocs during compilation */
MemoryContext compile_tmp_cxt;

/* ----------
 * Hash table for compiled functions
 * ----------
 */
static HTAB *plpgsql_HashTable = NULL;

typedef struct plpgsql_hashent
{
	PLpgSQL_func_hashkey key;
	PLpgSQL_function *function;
} plpgsql_HashEnt;

#define FUNCS_PER_USER		128 /* initial table size */

/* ----------
 * Lookup table for EXCEPTION condition names
 * ----------
 */
typedef struct
{
	const char *label;
	int			sqlerrstate;
} ExceptionLabelMap;

static const ExceptionLabelMap exception_label_map[] = {
#include "plerrcodes.h"
	{NULL, 0}
};


/* ----------
 * static prototypes
 * ----------
 */
static PLpgSQL_function *do_compile(FunctionCallInfo fcinfo,
		   HeapTuple procTup,
		   PLpgSQL_function *function,
		   PLpgSQL_func_hashkey *hashkey,
		   bool forValidator);
static PLpgSQL_row *build_row_from_class(Oid classOid);
static PLpgSQL_row *build_row_from_vars(PLpgSQL_variable **vars, int numvars);
static PLpgSQL_type *build_datatype(HeapTuple typeTup, int32 typmod);
static void compute_function_hashkey(FunctionCallInfo fcinfo,
						 Form_pg_proc procStruct,
						 PLpgSQL_func_hashkey *hashkey,
						 bool forValidator);
static void plpgsql_resolve_polymorphic_argtypes(int numargs,
									 Oid *argtypes, char *argmodes,
									 Node *call_expr, bool forValidator,
									 const char *proname);
static PLpgSQL_function *plpgsql_HashTableLookup(PLpgSQL_func_hashkey *func_key);
static void plpgsql_HashTableInsert(PLpgSQL_function *function,
						PLpgSQL_func_hashkey *func_key);
static void plpgsql_HashTableDelete(PLpgSQL_function *function);
static void delete_function(PLpgSQL_function *func);

/* ----------
 * plpgsql_compile		Make an execution tree for a PL/pgSQL function.
 *
 * If forValidator is true, we're only compiling for validation purposes,
 * and so some checks are skipped.
 *
 * Note: it's important for this to fall through quickly if the function
 * has already been compiled.
 * ----------
 */
PLpgSQL_function *
plpgsql_compile(FunctionCallInfo fcinfo, bool forValidator)
{
	Oid			funcOid = fcinfo->flinfo->fn_oid;
	HeapTuple	procTup;
	Form_pg_proc procStruct;
	PLpgSQL_function *function;
	PLpgSQL_func_hashkey hashkey;
	bool		function_valid = false;
	bool		hashkey_valid = false;

	/*
	 * Lookup the pg_proc tuple by Oid; we'll need it in any case
	 */
	procTup = SearchSysCache(PROCOID,
							 ObjectIdGetDatum(funcOid),
							 0, 0, 0);
	if (!HeapTupleIsValid(procTup))
		elog(ERROR, "cache lookup failed for function %u", funcOid);
	procStruct = (Form_pg_proc) GETSTRUCT(procTup);

	/*
	 * See if there's already a cache entry for the current FmgrInfo. If not,
	 * try to find one in the hash table.
	 */
	function = (PLpgSQL_function *) fcinfo->flinfo->fn_extra;

recheck:
	if (!function)
	{
		/* Compute hashkey using function signature and actual arg types */
		compute_function_hashkey(fcinfo, procStruct, &hashkey, forValidator);
		hashkey_valid = true;

		/* And do the lookup */
		function = plpgsql_HashTableLookup(&hashkey);
	}

	if (function)
	{
		/* We have a compiled function, but is it still valid? */
		if (function->fn_xmin == HeapTupleHeaderGetXmin(procTup->t_data) &&
			ItemPointerEquals(&function->fn_tid, &procTup->t_self))
			function_valid = true;
		else
		{
			/*
			 * Nope, so remove it from hashtable and try to drop associated
			 * storage (if not done already).
			 */
			delete_function(function);

			/*
			 * If the function isn't in active use then we can overwrite the
			 * func struct with new data, allowing any other existing fn_extra
			 * pointers to make use of the new definition on their next use.
			 * If it is in use then just leave it alone and make a new one.
			 * (The active invocations will run to completion using the
			 * previous definition, and then the cache entry will just be
			 * leaked; doesn't seem worth adding code to clean it up, given
			 * what a corner case this is.)
			 *
			 * If we found the function struct via fn_extra then it's possible
			 * a replacement has already been made, so go back and recheck the
			 * hashtable.
			 */
			if (function->use_count != 0)
			{
				function = NULL;
				if (!hashkey_valid)
					goto recheck;
			}
		}
	}

	/*
	 * If the function wasn't found or was out-of-date, we have to compile it
	 */
	if (!function_valid)
	{
		/*
		 * Calculate hashkey if we didn't already; we'll need it to store the
		 * completed function.
		 */
		if (!hashkey_valid)
			compute_function_hashkey(fcinfo, procStruct, &hashkey,
									 forValidator);

		/*
		 * Do the hard part.
		 */
		function = do_compile(fcinfo, procTup, function,
							  &hashkey, forValidator);
	}

	ReleaseSysCache(procTup);

	/*
	 * Save pointer in FmgrInfo to avoid search on subsequent calls
	 */
	fcinfo->flinfo->fn_extra = (void *) function;

	/*
	 * Finally return the compiled function
	 */
	return function;
}

/*
 * This is the slow part of plpgsql_compile().
 *
 * The passed-in "function" pointer is either NULL or an already-allocated
 * function struct to overwrite.
 *
 * While compiling a function, the CurrentMemoryContext is the
 * per-function memory context of the function we are compiling. That
 * means a palloc() will allocate storage with the same lifetime as
 * the function itself.
 *
 * Because palloc()'d storage will not be immediately freed, temporary
 * allocations should either be performed in a short-lived memory
 * context or explicitly pfree'd. Since not all backend functions are
 * careful about pfree'ing their allocations, it is also wise to
 * switch into a short-term context before calling into the
 * backend. An appropriate context for performing short-term
 * allocations is the compile_tmp_cxt.
 *
 * NB: this code is not re-entrant.  We assume that nothing we do here could
 * result in the invocation of another plpgsql function.
 */
static PLpgSQL_function *
do_compile(FunctionCallInfo fcinfo,
		   HeapTuple procTup,
		   PLpgSQL_function *function,
		   PLpgSQL_func_hashkey *hashkey,
		   bool forValidator)
{
	Form_pg_proc procStruct = (Form_pg_proc) GETSTRUCT(procTup);
	int			functype = CALLED_AS_TRIGGER(fcinfo) ? T_TRIGGER : T_FUNCTION;
	Datum		prosrcdatum;
	bool		isnull;
	char	   *proc_source;
	HeapTuple	typeTup;
	Form_pg_type typeStruct;
	PLpgSQL_variable *var;
	PLpgSQL_rec *rec;
	int			i;
	ErrorContextCallback plerrcontext;
	int			parse_rc;
	Oid			rettypeid;
	int			numargs;
	int			num_in_args = 0;
	int			num_out_args = 0;
	Oid		   *argtypes;
	char	  **argnames;
	char	   *argmodes;
	int		   *in_arg_varnos = NULL;
	PLpgSQL_variable **out_arg_variables;
	MemoryContext func_cxt;

	/*
	 * Setup the scanner input and error info.	We assume that this function
	 * cannot be invoked recursively, so there's no need to save and restore
	 * the static variables used here.
	 */
	prosrcdatum = SysCacheGetAttr(PROCOID, procTup,
								  Anum_pg_proc_prosrc, &isnull);
	if (isnull)
		elog(ERROR, "null prosrc");
	proc_source = DatumGetCString(DirectFunctionCall1(textout, prosrcdatum));
	plpgsql_scanner_init(proc_source, functype);

	plpgsql_error_funcname = pstrdup(NameStr(procStruct->proname));
	plpgsql_error_lineno = 0;

	/*
	 * Setup error traceback support for ereport()
	 */
	plerrcontext.callback = plpgsql_compile_error_callback;
	plerrcontext.arg = forValidator ? proc_source : NULL;
	plerrcontext.previous = error_context_stack;
	error_context_stack = &plerrcontext;

	/*
	 * Initialize the compiler, particularly the namespace stack.  The
	 * outermost namespace contains function parameters and other special
	 * variables (such as FOUND), and is named after the function itself.
	 */
	plpgsql_ns_init();
	plpgsql_ns_push(NameStr(procStruct->proname));
	plpgsql_DumpExecTree = false;

	datums_alloc = 128;
	plpgsql_nDatums = 0;
	/* This is short-lived, so needn't allocate in function's cxt */
	plpgsql_Datums = palloc(sizeof(PLpgSQL_datum *) * datums_alloc);
	datums_last = 0;

	/*
	 * Do extra syntax checks when validating the function definition. We skip
	 * this when actually compiling functions for execution, for performance
	 * reasons.
	 */
	plpgsql_check_syntax = forValidator;

	/*
	 * Create the new function struct, if not done already.  The function
	 * structs are never thrown away, so keep them in TopMemoryContext.
	 */
	if (function == NULL)
	{
		function = (PLpgSQL_function *)
			MemoryContextAllocZero(TopMemoryContext, sizeof(PLpgSQL_function));
	}
	else
	{
		/* re-using a previously existing struct, so clear it out */
		memset(function, 0, sizeof(PLpgSQL_function));
	}
	plpgsql_curr_compile = function;

	/*
	 * All the rest of the compile-time storage (e.g. parse tree) is kept in
	 * its own memory context, so it can be reclaimed easily.
	 */
	func_cxt = AllocSetContextCreate(TopMemoryContext,
									 "PL/PgSQL function context",
									 ALLOCSET_DEFAULT_MINSIZE,
									 ALLOCSET_DEFAULT_INITSIZE,
									 ALLOCSET_DEFAULT_MAXSIZE);
	compile_tmp_cxt = MemoryContextSwitchTo(func_cxt);

	function->fn_name = pstrdup(NameStr(procStruct->proname));
	function->fn_oid = fcinfo->flinfo->fn_oid;
	function->fn_xmin = HeapTupleHeaderGetXmin(procTup->t_data);
	function->fn_tid = procTup->t_self;
	function->fn_functype = functype;
	function->fn_cxt = func_cxt;
	function->out_param_varno = -1;		/* set up for no OUT param */

	switch (functype)
	{
		case T_FUNCTION:

			/*
			 * Fetch info about the procedure's parameters. Allocations aren't
			 * needed permanently, so make them in tmp cxt.
			 *
			 * We also need to resolve any polymorphic input or output
			 * argument types.	In validation mode we won't be able to, so we
			 * arbitrarily assume we are dealing with integers.
			 */
			MemoryContextSwitchTo(compile_tmp_cxt);

			numargs = get_func_arg_info(procTup,
										&argtypes, &argnames, &argmodes);

			plpgsql_resolve_polymorphic_argtypes(numargs, argtypes, argmodes,
												 fcinfo->flinfo->fn_expr,
												 forValidator,
												 plpgsql_error_funcname);

			in_arg_varnos = (int *) palloc(numargs * sizeof(int));
			out_arg_variables = (PLpgSQL_variable **) palloc(numargs * sizeof(PLpgSQL_variable *));

			MemoryContextSwitchTo(func_cxt);

			/*
			 * Create the variables for the procedure's parameters.
			 */
			for (i = 0; i < numargs; i++)
			{
				char		buf[32];
				Oid			argtypeid = argtypes[i];
				char		argmode = argmodes ? argmodes[i] : PROARGMODE_IN;
				PLpgSQL_type *argdtype;
				PLpgSQL_variable *argvariable;
				int			argitemtype;

				/* Create $n name for variable */
				snprintf(buf, sizeof(buf), "$%d", i + 1);

				/* Create datatype info */
				argdtype = plpgsql_build_datatype(argtypeid, -1);

				/* Disallow pseudotype argument */
				/* (note we already replaced polymorphic types) */
				/* (build_variable would do this, but wrong message) */
				if (argdtype->ttype != PLPGSQL_TTYPE_SCALAR &&
					argdtype->ttype != PLPGSQL_TTYPE_ROW)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("plpgsql functions cannot take type %s",
									format_type_be(argtypeid))));

				/* Build variable and add to datum list */
				argvariable = plpgsql_build_variable(buf, 0,
													 argdtype, false);

				if (argvariable->dtype == PLPGSQL_DTYPE_VAR)
				{
					argitemtype = PLPGSQL_NSTYPE_VAR;
					/* input argument vars are forced to be CONSTANT */
					if (argmode == PROARGMODE_IN)
						((PLpgSQL_var *) argvariable)->isconst = true;
				}
				else
				{
					Assert(argvariable->dtype == PLPGSQL_DTYPE_ROW);
					argitemtype = PLPGSQL_NSTYPE_ROW;
				}

				/* Remember arguments in appropriate arrays */
				if (argmode == PROARGMODE_IN || argmode == PROARGMODE_INOUT)
					in_arg_varnos[num_in_args++] = argvariable->dno;
				if (argmode == PROARGMODE_OUT || argmode == PROARGMODE_INOUT)
					out_arg_variables[num_out_args++] = argvariable;

				/* Add to namespace under the $n name */
				plpgsql_ns_additem(argitemtype, argvariable->dno, buf);

				/* If there's a name for the argument, make an alias */
				if (argnames && argnames[i][0] != '\0')
					plpgsql_ns_additem(argitemtype, argvariable->dno,
									   argnames[i]);
			}

			/*
			 * If there's just one OUT parameter, out_param_varno points
			 * directly to it.	If there's more than one, build a row that
			 * holds all of them.
			 */
			if (num_out_args == 1)
				function->out_param_varno = out_arg_variables[0]->dno;
			else if (num_out_args > 1)
			{
				PLpgSQL_row *row = build_row_from_vars(out_arg_variables,
													   num_out_args);

				plpgsql_adddatum((PLpgSQL_datum *) row);
				function->out_param_varno = row->rowno;
			}

			/*
			 * Check for a polymorphic returntype. If found, use the actual
			 * returntype type from the caller's FuncExpr node, if we have
			 * one.  (In validation mode we arbitrarily assume we are dealing
			 * with integers.)
			 *
			 * Note: errcode is FEATURE_NOT_SUPPORTED because it should always
			 * work; if it doesn't we're in some context that fails to make
			 * the info available.
			 */
			rettypeid = procStruct->prorettype;
			if (IsPolymorphicType(rettypeid))
			{
				if (forValidator)
				{
					if (rettypeid == ANYARRAYOID)
						rettypeid = INT4ARRAYOID;
					else	/* ANYELEMENT or ANYNONARRAY */
						rettypeid = INT4OID;
					/* XXX what could we use for ANYENUM? */
				}
				else
				{
					rettypeid = get_fn_expr_rettype(fcinfo->flinfo);
					if (!OidIsValid(rettypeid))
						ereport(ERROR,
								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("could not determine actual return type "
									"for polymorphic function \"%s\"",
									plpgsql_error_funcname)));
				}
			}

			/*
			 * Normal function has a defined returntype
			 */
			function->fn_rettype = rettypeid;
			function->fn_retset = procStruct->proretset;

			/*
			 * Lookup the function's return type
			 */
			typeTup = SearchSysCache(TYPEOID,
									 ObjectIdGetDatum(rettypeid),
									 0, 0, 0);
			if (!HeapTupleIsValid(typeTup))
				elog(ERROR, "cache lookup failed for type %u", rettypeid);
			typeStruct = (Form_pg_type) GETSTRUCT(typeTup);

			/* Disallow pseudotype result, except VOID or RECORD */
			/* (note we already replaced polymorphic types) */
			if (typeStruct->typtype == TYPTYPE_PSEUDO)
			{