pl_exec.c

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/*-------------------------------------------------------------------------
 *
 * pl_exec.c		- Executor for 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_exec.c,v 1.202.2.1 2008/09/01 22:30:40 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "plpgsql.h"
#include "pl.tab.h"

#include <ctype.h>

#include "access/heapam.h"
#include "access/transam.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "executor/spi_priv.h"
#include "funcapi.h"
#include "optimizer/clauses.h"
#include "parser/parse_expr.h"
#include "parser/scansup.h"
#include "tcop/tcopprot.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/typcache.h"


static const char *const raise_skip_msg = "RAISE";

/*
 * All plpgsql function executions within a single transaction share the same
 * executor EState for evaluating "simple" expressions.  Each function call
 * creates its own "eval_econtext" ExprContext within this estate for
 * per-evaluation workspace.  eval_econtext is freed at normal function exit,
 * and the EState is freed at transaction end (in case of error, we assume
 * that the abort mechanisms clean it all up).	In order to be sure
 * ExprContext callbacks are handled properly, each subtransaction has to have
 * its own such EState; hence we need a stack.	We use a simple counter to
 * distinguish different instantiations of the EState, so that we can tell
 * whether we have a current copy of a prepared expression.
 *
 * This arrangement is a bit tedious to maintain, but it's worth the trouble
 * so that we don't have to re-prepare simple expressions on each trip through
 * a function.	(We assume the case to optimize is many repetitions of a
 * function within a transaction.)
 */
typedef struct SimpleEstateStackEntry
{
	EState	   *xact_eval_estate;		/* EState for current xact level */
	long int	xact_estate_simple_id;	/* ID for xact_eval_estate */
	SubTransactionId xact_subxid;		/* ID for current subxact */
	struct SimpleEstateStackEntry *next;		/* next stack entry up */
} SimpleEstateStackEntry;

static SimpleEstateStackEntry *simple_estate_stack = NULL;
static long int simple_estate_id_counter = 0;

/************************************************************
 * Local function forward declarations
 ************************************************************/
static void plpgsql_exec_error_callback(void *arg);
static PLpgSQL_datum *copy_plpgsql_datum(PLpgSQL_datum *datum);

static int exec_stmt_block(PLpgSQL_execstate *estate,
				PLpgSQL_stmt_block *block);
static int exec_stmts(PLpgSQL_execstate *estate,
		   List *stmts);
static int exec_stmt(PLpgSQL_execstate *estate,
		  PLpgSQL_stmt *stmt);
static int exec_stmt_assign(PLpgSQL_execstate *estate,
				 PLpgSQL_stmt_assign *stmt);
static int exec_stmt_perform(PLpgSQL_execstate *estate,
				  PLpgSQL_stmt_perform *stmt);
static int exec_stmt_getdiag(PLpgSQL_execstate *estate,
				  PLpgSQL_stmt_getdiag *stmt);
static int exec_stmt_if(PLpgSQL_execstate *estate,
			 PLpgSQL_stmt_if *stmt);
static int exec_stmt_loop(PLpgSQL_execstate *estate,
			   PLpgSQL_stmt_loop *stmt);
static int exec_stmt_while(PLpgSQL_execstate *estate,
				PLpgSQL_stmt_while *stmt);
static int exec_stmt_fori(PLpgSQL_execstate *estate,
			   PLpgSQL_stmt_fori *stmt);
static int exec_stmt_fors(PLpgSQL_execstate *estate,
			   PLpgSQL_stmt_fors *stmt);
static int exec_stmt_open(PLpgSQL_execstate *estate,
			   PLpgSQL_stmt_open *stmt);
static int exec_stmt_fetch(PLpgSQL_execstate *estate,
				PLpgSQL_stmt_fetch *stmt);
static int exec_stmt_close(PLpgSQL_execstate *estate,
				PLpgSQL_stmt_close *stmt);
static int exec_stmt_exit(PLpgSQL_execstate *estate,
			   PLpgSQL_stmt_exit *stmt);
static int exec_stmt_return(PLpgSQL_execstate *estate,
				 PLpgSQL_stmt_return *stmt);
static int exec_stmt_return_next(PLpgSQL_execstate *estate,
					  PLpgSQL_stmt_return_next *stmt);
static int exec_stmt_return_query(PLpgSQL_execstate *estate,
					   PLpgSQL_stmt_return_query *stmt);
static int exec_stmt_raise(PLpgSQL_execstate *estate,
				PLpgSQL_stmt_raise *stmt);
static int exec_stmt_execsql(PLpgSQL_execstate *estate,
				  PLpgSQL_stmt_execsql *stmt);
static int exec_stmt_dynexecute(PLpgSQL_execstate *estate,
					 PLpgSQL_stmt_dynexecute *stmt);
static int exec_stmt_dynfors(PLpgSQL_execstate *estate,
				  PLpgSQL_stmt_dynfors *stmt);

static void plpgsql_estate_setup(PLpgSQL_execstate *estate,
					 PLpgSQL_function *func,
					 ReturnSetInfo *rsi);
static void exec_eval_cleanup(PLpgSQL_execstate *estate);

static void exec_prepare_plan(PLpgSQL_execstate *estate,
				  PLpgSQL_expr *expr, int cursorOptions);
static bool exec_simple_check_node(Node *node);
static void exec_simple_check_plan(PLpgSQL_expr *expr);
static bool exec_eval_simple_expr(PLpgSQL_execstate *estate,
					  PLpgSQL_expr *expr,
					  Datum *result,
					  bool *isNull,
					  Oid *rettype);

static void exec_assign_expr(PLpgSQL_execstate *estate,
				 PLpgSQL_datum *target,
				 PLpgSQL_expr *expr);
static void exec_assign_value(PLpgSQL_execstate *estate,
				  PLpgSQL_datum *target,
				  Datum value, Oid valtype, bool *isNull);
static void exec_eval_datum(PLpgSQL_execstate *estate,
				PLpgSQL_datum *datum,
				Oid expectedtypeid,
				Oid *typeid,
				Datum *value,
				bool *isnull);
static int exec_eval_integer(PLpgSQL_execstate *estate,
				  PLpgSQL_expr *expr,
				  bool *isNull);
static bool exec_eval_boolean(PLpgSQL_execstate *estate,
				  PLpgSQL_expr *expr,
				  bool *isNull);
static Datum exec_eval_expr(PLpgSQL_execstate *estate,
			   PLpgSQL_expr *expr,
			   bool *isNull,
			   Oid *rettype);
static int exec_run_select(PLpgSQL_execstate *estate,
				PLpgSQL_expr *expr, long maxtuples, Portal *portalP);
static void exec_move_row(PLpgSQL_execstate *estate,
			  PLpgSQL_rec *rec,
			  PLpgSQL_row *row,
			  HeapTuple tup, TupleDesc tupdesc);
static HeapTuple make_tuple_from_row(PLpgSQL_execstate *estate,
					PLpgSQL_row *row,
					TupleDesc tupdesc);
static char *convert_value_to_string(Datum value, Oid valtype);
static Datum exec_cast_value(Datum value, Oid valtype,
				Oid reqtype,
				FmgrInfo *reqinput,
				Oid reqtypioparam,
				int32 reqtypmod,
				bool isnull);
static Datum exec_simple_cast_value(Datum value, Oid valtype,
					   Oid reqtype, int32 reqtypmod,
					   bool isnull);
static void exec_init_tuple_store(PLpgSQL_execstate *estate);
static bool compatible_tupdesc(TupleDesc td1, TupleDesc td2);
static void exec_set_found(PLpgSQL_execstate *estate, bool state);
static void plpgsql_create_econtext(PLpgSQL_execstate *estate);
static void free_var(PLpgSQL_var *var);


/* ----------
 * plpgsql_exec_function	Called by the call handler for
 *				function execution.
 * ----------
 */
Datum
plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo)
{
	PLpgSQL_execstate estate;
	ErrorContextCallback plerrcontext;
	int			i;
	int			rc;

	/*
	 * Setup the execution state
	 */
	plpgsql_estate_setup(&estate, func, (ReturnSetInfo *) fcinfo->resultinfo);

	/*
	 * Setup error traceback support for ereport()
	 */
	plerrcontext.callback = plpgsql_exec_error_callback;
	plerrcontext.arg = &estate;
	plerrcontext.previous = error_context_stack;
	error_context_stack = &plerrcontext;

	/*
	 * Make local execution copies of all the datums
	 */
	estate.err_text = gettext_noop("during initialization of execution state");
	for (i = 0; i < estate.ndatums; i++)
		estate.datums[i] = copy_plpgsql_datum(func->datums[i]);

	/*
	 * Store the actual call argument values into the appropriate variables
	 */
	estate.err_text = gettext_noop("while storing call arguments into local variables");
	for (i = 0; i < func->fn_nargs; i++)
	{
		int			n = func->fn_argvarnos[i];

		switch (estate.datums[n]->dtype)
		{
			case PLPGSQL_DTYPE_VAR:
				{
					PLpgSQL_var *var = (PLpgSQL_var *) estate.datums[n];

					var->value = fcinfo->arg[i];
					var->isnull = fcinfo->argnull[i];
					var->freeval = false;
				}
				break;

			case PLPGSQL_DTYPE_ROW:
				{
					PLpgSQL_row *row = (PLpgSQL_row *) estate.datums[n];

					if (!fcinfo->argnull[i])
					{
						HeapTupleHeader td;
						Oid			tupType;
						int32		tupTypmod;
						TupleDesc	tupdesc;
						HeapTupleData tmptup;

						td = DatumGetHeapTupleHeader(fcinfo->arg[i]);
						/* Extract rowtype info and find a tupdesc */
						tupType = HeapTupleHeaderGetTypeId(td);
						tupTypmod = HeapTupleHeaderGetTypMod(td);
						tupdesc = lookup_rowtype_tupdesc(tupType, tupTypmod);
						/* Build a temporary HeapTuple control structure */
						tmptup.t_len = HeapTupleHeaderGetDatumLength(td);
						ItemPointerSetInvalid(&(tmptup.t_self));
						tmptup.t_tableOid = InvalidOid;
						tmptup.t_data = td;
						exec_move_row(&estate, NULL, row, &tmptup, tupdesc);
						ReleaseTupleDesc(tupdesc);
					}
					else
					{
						/* If arg is null, treat it as an empty row */
						exec_move_row(&estate, NULL, row, NULL, NULL);
					}
				}
				break;

			default:
				elog(ERROR, "unrecognized dtype: %d", func->datums[i]->dtype);
		}
	}

	estate.err_text = gettext_noop("during function entry");

	/*
	 * Set the magic variable FOUND to false
	 */
	exec_set_found(&estate, false);

	/*
	 * Let the instrumentation plugin peek at this function
	 */
	if (*plugin_ptr && (*plugin_ptr)->func_beg)
		((*plugin_ptr)->func_beg) (&estate, func);

	/*
	 * Now call the toplevel block of statements
	 */
	estate.err_text = NULL;
	estate.err_stmt = (PLpgSQL_stmt *) (func->action);
	rc = exec_stmt_block(&estate, func->action);
	if (rc != PLPGSQL_RC_RETURN)
	{
		estate.err_stmt = NULL;
		estate.err_text = NULL;

		/*
		 * Provide a more helpful message if a CONTINUE has been used outside
		 * a loop.
		 */
		if (rc == PLPGSQL_RC_CONTINUE)
			ereport(ERROR,
					(errcode(ERRCODE_SYNTAX_ERROR),
					 errmsg("CONTINUE cannot be used outside a loop")));
		else
			ereport(ERROR,
			   (errcode(ERRCODE_S_R_E_FUNCTION_EXECUTED_NO_RETURN_STATEMENT),
				errmsg("control reached end of function without RETURN")));
	}

	/*
	 * We got a return value - process it
	 */
	estate.err_stmt = NULL;
	estate.err_text = gettext_noop("while casting return value to function's return type");

	fcinfo->isnull = estate.retisnull;

	if (estate.retisset)
	{
		ReturnSetInfo *rsi = estate.rsi;

		/* Check caller can handle a set result */
		if (!rsi || !IsA(rsi, ReturnSetInfo) ||
			(rsi->allowedModes & SFRM_Materialize) == 0)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("set-valued function called in context that cannot accept a set")));
		rsi->returnMode = SFRM_Materialize;

		/* If we produced any tuples, send back the result */
		if (estate.tuple_store)
		{
			rsi->setResult = estate.tuple_store;
			if (estate.rettupdesc)
			{
				MemoryContext oldcxt;

				oldcxt = MemoryContextSwitchTo(estate.tuple_store_cxt);
				rsi->setDesc = CreateTupleDescCopy(estate.rettupdesc);
				MemoryContextSwitchTo(oldcxt);
			}
		}
		estate.retval = (Datum) 0;
		fcinfo->isnull = true;
	}
	else if (!estate.retisnull)
	{
		if (estate.retistuple)
		{
			/*
			 * We have to check that the returned tuple actually matches the
			 * expected result type.  XXX would be better to cache the tupdesc
			 * instead of repeating get_call_result_type()
			 */
			TupleDesc	tupdesc;

			switch (get_call_result_type(fcinfo, NULL, &tupdesc))
			{
				case TYPEFUNC_COMPOSITE:
					/* got the expected result rowtype, now check it */
					if (estate.rettupdesc == NULL ||
						!compatible_tupdesc(estate.rettupdesc, tupdesc))
						ereport(ERROR,
								(errcode(ERRCODE_DATATYPE_MISMATCH),
								 errmsg("returned record type does not match expected record type")));
					break;
				case TYPEFUNC_RECORD:

					/*
					 * Failed to determine actual type of RECORD.  We could
					 * raise an error here, but what this means in practice is
					 * that the caller is expecting any old generic rowtype,
					 * so we don't really need to be restrictive. Pass back
					 * the generated result type, instead.
					 */
					tupdesc = estate.rettupdesc;
					if (tupdesc == NULL)		/* shouldn't happen */
						elog(ERROR, "return type must be a row type");
					break;
				default:
					/* shouldn't get here if retistuple is true ... */
					elog(ERROR, "return type must be a row type");
					break;
			}

			/*
			 * Copy tuple to upper executor memory, as a tuple Datum. Make
			 * sure it is labeled with the caller-supplied tuple type.
			 */
			estate.retval =
				PointerGetDatum(SPI_returntuple((HeapTuple) (estate.retval),
												tupdesc));
		}
		else
		{
			/* Cast value to proper type */
			estate.retval = exec_cast_value(estate.retval, estate.rettype,
											func->fn_rettype,
											&(func->fn_retinput),
											func->fn_rettypioparam,
											-1,
											fcinfo->isnull);

			/*
			 * If the function's return type isn't by value, copy the value
			 * into upper executor memory context.
			 */
			if (!fcinfo->isnull && !func->fn_retbyval)
			{
				Size		len;
				void	   *tmp;

				len = datumGetSize(estate.retval, false, func->fn_rettyplen);
				tmp = SPI_palloc(len);
				memcpy(tmp, DatumGetPointer(estate.retval), len);
				estate.retval = PointerGetDatum(tmp);
			}
		}
	}

	estate.err_text = gettext_noop("during function exit");

	/*
	 * Let the instrumentation plugin peek at this function
	 */
	if (*plugin_ptr && (*plugin_ptr)->func_end)
		((*plugin_ptr)->func_end) (&estate, func);

	/* Clean up any leftover temporary memory */
	FreeExprContext(estate.eval_econtext);
	estate.eval_econtext = NULL;
	exec_eval_cleanup(&estate);

	/*
	 * Pop the error context stack
	 */
	error_context_stack = plerrcontext.previous;

	/*
	 * Return the function's result
	 */
	return estate.retval;
}


/* ----------
 * plpgsql_exec_trigger		Called by the call handler for
 *				trigger execution.
 * ----------
 */
HeapTuple
plpgsql_exec_trigger(PLpgSQL_function *func,
					 TriggerData *trigdata)
{
	PLpgSQL_execstate estate;
	ErrorContextCallback plerrcontext;
	int			i;
	int			rc;
	PLpgSQL_var *var;
	PLpgSQL_rec *rec_new,
			   *rec_old;
	HeapTuple	rettup;

	/*
	 * Setup the execution state
	 */
	plpgsql_estate_setup(&estate, func, NULL);

	/*
	 * Setup error traceback support for ereport()
	 */
	plerrcontext.callback = plpgsql_exec_error_callback;
	plerrcontext.arg = &estate;
	plerrcontext.previous = error_context_stack;
	error_context_stack = &plerrcontext;

	/*
	 * Make local execution copies of all the datums
	 */
	estate.err_text = gettext_noop("during initialization of execution state");
	for (i = 0; i < estate.ndatums; i++)
		estate.datums[i] = copy_plpgsql_datum(func->datums[i]);

	/*
	 * Put the OLD and NEW tuples into record variables
	 */
	rec_new = (PLpgSQL_rec *) (estate.datums[func->new_varno]);
	rec_new->freetup = false;
	rec_new->freetupdesc = false;
	rec_old = (PLpgSQL_rec *) (estate.datums[func->old_varno]);
	rec_old->freetup = false;
	rec_old->freetupdesc = false;

	if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
	{
		/*
		 * Per-statement triggers don't use OLD/NEW variables
		 */
		rec_new->tup = NULL;
		rec_new->tupdesc = NULL;
		rec_old->tup = NULL;
		rec_old->tupdesc = NULL;
	}
	else if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))