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Redesign query-snapshot timing so that volatile functions in READ COMMITTED
mode see a fresh snapshot for each command in the function, rather than using the latest interactive command's snapshot. Also, suppress fresh snapshots as well as CommandCounterIncrement inside STABLE and IMMUTABLE functions, instead using the snapshot taken for the most closely nested regular query. (This behavior is only sane for read-only functions, so the patch also enforces that such functions contain only SELECT commands.) As per my proposal of 6-Sep-2004; I note that I floated essentially the same proposal on 19-Jun-2002, but that discussion tailed off without any action. Since 8.0 seems like the right place to be taking possibly nontrivial backwards compatibility hits, let's get it done now.
This commit is contained in:
Tom Lane
@ -31,7 +31,7 @@
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* ENHANCEMENTS, OR MODIFICATIONS.
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.91 2004/08/30 02:54:42 momjian Exp $
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* $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.92 2004/09/13 20:09:39 tgl Exp $
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*
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**********************************************************************/
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@ -87,13 +87,17 @@ utf_e2u(unsigned char *src)
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pfree(_pltcl_utf_dst); } while (0)
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#define UTF_U2E(x) (_pltcl_utf_dst=utf_u2e(_pltcl_utf_src=(x)))
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#define UTF_E2U(x) (_pltcl_utf_dst=utf_e2u(_pltcl_utf_src=(x)))
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#else /* PLTCL_UTF */
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#else /* !PLTCL_UTF */
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#define UTF_BEGIN
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#define UTF_END
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#define UTF_U2E(x) (x)
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#define UTF_E2U(x) (x)
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#endif /* PLTCL_UTF */
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/**********************************************************************
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* The information we cache about loaded procedures
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**********************************************************************/
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@ -102,6 +106,7 @@ typedef struct pltcl_proc_desc
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char *proname;
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TransactionId fn_xmin;
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CommandId fn_cmin;
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bool fn_readonly;
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bool lanpltrusted;
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FmgrInfo result_in_func;
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Oid result_typioparam;
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@ -137,7 +142,10 @@ static Tcl_Interp *pltcl_safe_interp = NULL;
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static Tcl_HashTable *pltcl_proc_hash = NULL;
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static Tcl_HashTable *pltcl_norm_query_hash = NULL;
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static Tcl_HashTable *pltcl_safe_query_hash = NULL;
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/* these are saved and restored by pltcl_call_handler */
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static FunctionCallInfo pltcl_current_fcinfo = NULL;
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static pltcl_proc_desc *pltcl_current_prodesc = NULL;
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/*
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* When a callback from Tcl into PG incurs an error, we temporarily store
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@ -179,11 +187,11 @@ static int pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
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static int pltcl_returnnull(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[]);
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static int pltcl_SPI_exec(ClientData cdata, Tcl_Interp *interp,
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static int pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[]);
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static int pltcl_SPI_prepare(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[]);
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static int pltcl_SPI_execp(ClientData cdata, Tcl_Interp *interp,
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static int pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[]);
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static int pltcl_SPI_lastoid(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[]);
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@ -307,11 +315,11 @@ pltcl_init_interp(Tcl_Interp *interp)
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pltcl_returnnull, NULL, NULL);
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Tcl_CreateCommand(interp, "spi_exec",
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pltcl_SPI_exec, NULL, NULL);
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pltcl_SPI_execute, NULL, NULL);
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Tcl_CreateCommand(interp, "spi_prepare",
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pltcl_SPI_prepare, NULL, NULL);
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Tcl_CreateCommand(interp, "spi_execp",
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pltcl_SPI_execp, NULL, NULL);
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pltcl_SPI_execute_plan, NULL, NULL);
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Tcl_CreateCommand(interp, "spi_lastoid",
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pltcl_SPI_lastoid, NULL, NULL);
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}
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@ -334,8 +342,9 @@ pltcl_init_load_unknown(Tcl_Interp *interp)
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/************************************************************
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* Check if table pltcl_modules exists
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************************************************************/
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spi_rc = SPI_exec("select 1 from pg_catalog.pg_class "
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"where relname = 'pltcl_modules'", 1);
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spi_rc = SPI_execute("select 1 from pg_catalog.pg_class "
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"where relname = 'pltcl_modules'",
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false, 1);
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SPI_freetuptable(SPI_tuptable);
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if (spi_rc != SPI_OK_SELECT)
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elog(ERROR, "select from pg_class failed");
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@ -348,9 +357,10 @@ pltcl_init_load_unknown(Tcl_Interp *interp)
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************************************************************/
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Tcl_DStringInit(&unknown_src);
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spi_rc = SPI_exec("select modseq, modsrc from pltcl_modules "
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"where modname = 'unknown' "
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"order by modseq", 0);
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spi_rc = SPI_execute("select modseq, modsrc from pltcl_modules "
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"where modname = 'unknown' "
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"order by modseq",
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false, 0);
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if (spi_rc != SPI_OK_SELECT)
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elog(ERROR, "select from pltcl_modules failed");
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@ -405,30 +415,46 @@ pltcl_call_handler(PG_FUNCTION_ARGS)
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{
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Datum retval;
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FunctionCallInfo save_fcinfo;
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pltcl_proc_desc *save_prodesc;
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/************************************************************
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/*
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* Initialize interpreters if first time through
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************************************************************/
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*/
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pltcl_init_all();
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/************************************************************
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* Determine if called as function or trigger and
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* call appropriate subhandler
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************************************************************/
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/*
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* Ensure that static pointers are saved/restored properly
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*/
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save_fcinfo = pltcl_current_fcinfo;
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save_prodesc = pltcl_current_prodesc;
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if (CALLED_AS_TRIGGER(fcinfo))
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PG_TRY();
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{
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pltcl_current_fcinfo = NULL;
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retval = PointerGetDatum(pltcl_trigger_handler(fcinfo));
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/*
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* Determine if called as function or trigger and
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* call appropriate subhandler
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*/
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if (CALLED_AS_TRIGGER(fcinfo))
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{
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pltcl_current_fcinfo = NULL;
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retval = PointerGetDatum(pltcl_trigger_handler(fcinfo));
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}
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else
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{
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pltcl_current_fcinfo = fcinfo;
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retval = pltcl_func_handler(fcinfo);
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}
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}
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else
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PG_CATCH();
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{
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pltcl_current_fcinfo = fcinfo;
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retval = pltcl_func_handler(fcinfo);
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pltcl_current_fcinfo = save_fcinfo;
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pltcl_current_prodesc = save_prodesc;
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PG_RE_THROW();
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}
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PG_END_TRY();
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pltcl_current_fcinfo = save_fcinfo;
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pltcl_current_prodesc = save_prodesc;
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return retval;
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}
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@ -467,6 +493,8 @@ pltcl_func_handler(PG_FUNCTION_ARGS)
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/* Find or compile the function */
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prodesc = compile_pltcl_function(fcinfo->flinfo->fn_oid, InvalidOid);
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pltcl_current_prodesc = prodesc;
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if (prodesc->lanpltrusted)
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interp = pltcl_safe_interp;
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else
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@ -643,6 +671,8 @@ pltcl_trigger_handler(PG_FUNCTION_ARGS)
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prodesc = compile_pltcl_function(fcinfo->flinfo->fn_oid,
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RelationGetRelid(trigdata->tg_relation));
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pltcl_current_prodesc = prodesc;
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if (prodesc->lanpltrusted)
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interp = pltcl_safe_interp;
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else
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@ -1030,6 +1060,10 @@ compile_pltcl_function(Oid fn_oid, Oid tgreloid)
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prodesc->fn_xmin = HeapTupleHeaderGetXmin(procTup->t_data);
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prodesc->fn_cmin = HeapTupleHeaderGetCmin(procTup->t_data);
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/* Remember if function is STABLE/IMMUTABLE */
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prodesc->fn_readonly =
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(procStruct->provolatile != PROVOLATILE_VOLATILE);
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/************************************************************
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* Lookup the pg_language tuple by Oid
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************************************************************/
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@ -1336,7 +1370,7 @@ pltcl_elog(ClientData cdata, Tcl_Interp *interp,
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/**********************************************************************
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* pltcl_quote() - quote literal strings that are to
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* be used in SPI_exec query strings
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* be used in SPI_execute query strings
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**********************************************************************/
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static int
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pltcl_quote(ClientData cdata, Tcl_Interp *interp,
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@ -1484,12 +1518,12 @@ pltcl_returnnull(ClientData cdata, Tcl_Interp *interp,
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/**********************************************************************
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* pltcl_SPI_exec() - The builtin SPI_exec command
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* pltcl_SPI_execute() - The builtin SPI_execute command
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* for the Tcl interpreter
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**********************************************************************/
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static int
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pltcl_SPI_exec(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[])
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pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[])
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{
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volatile int my_rc;
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int spi_rc;
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@ -1570,7 +1604,8 @@ pltcl_SPI_exec(ClientData cdata, Tcl_Interp *interp,
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PG_TRY();
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{
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UTF_BEGIN;
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spi_rc = SPI_exec(UTF_U2E(argv[query_idx]), count);
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spi_rc = SPI_execute(UTF_U2E(argv[query_idx]),
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pltcl_current_prodesc->fn_readonly, count);
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UTF_END;
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}
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PG_CATCH();
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@ -1603,7 +1638,7 @@ pltcl_SPI_exec(ClientData cdata, Tcl_Interp *interp,
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break;
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default:
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Tcl_AppendResult(interp, "pltcl: SPI_exec failed: ",
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Tcl_AppendResult(interp, "pltcl: SPI_execute failed: ",
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SPI_result_code_string(spi_rc), NULL);
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SPI_freetuptable(SPI_tuptable);
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return TCL_ERROR;
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@ -1840,11 +1875,11 @@ pltcl_SPI_prepare(ClientData cdata, Tcl_Interp *interp,
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/**********************************************************************
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* pltcl_SPI_execp() - Execute a prepared plan
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* pltcl_SPI_execute_plan() - Execute a prepared plan
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**********************************************************************/
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static int
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pltcl_SPI_execp(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[])
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pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
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int argc, CONST84 char *argv[])
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{
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volatile int my_rc;
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int spi_rc;
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@ -1992,7 +2027,7 @@ pltcl_SPI_execp(ClientData cdata, Tcl_Interp *interp,
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}
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/************************************************************
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* Setup the value array for the SPI_execp() using
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* Setup the value array for SPI_execute_plan() using
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* the type specific input functions
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************************************************************/
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oldcontext = CurrentMemoryContext;
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@ -2046,7 +2081,10 @@ pltcl_SPI_execp(ClientData cdata, Tcl_Interp *interp,
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************************************************************/
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oldcontext = CurrentMemoryContext;
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PG_TRY();
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spi_rc = SPI_execp(qdesc->plan, argvalues, nulls, count);
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{
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spi_rc = SPI_execute_plan(qdesc->plan, argvalues, nulls,
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pltcl_current_prodesc->fn_readonly, count);
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}
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PG_CATCH();
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{
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MemoryContextSwitchTo(oldcontext);
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@ -2058,7 +2096,7 @@ pltcl_SPI_execp(ClientData cdata, Tcl_Interp *interp,
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PG_END_TRY();
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/************************************************************
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* Check the return code from SPI_execp()
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* Check the return code from SPI_execute_plan()
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************************************************************/
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switch (spi_rc)
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{
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@ -2080,7 +2118,7 @@ pltcl_SPI_execp(ClientData cdata, Tcl_Interp *interp,
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break;
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default:
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Tcl_AppendResult(interp, "pltcl: SPI_execp failed: ",
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Tcl_AppendResult(interp, "pltcl: SPI_execute_plan failed: ",
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SPI_result_code_string(spi_rc), NULL);
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SPI_freetuptable(SPI_tuptable);
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return TCL_ERROR;
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