From 21dcda2713656a7483e3280ac9d2ada20a87a9a9 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 11 Mar 2015 12:40:43 -0400
Subject: [PATCH] Allocate ParamListInfo once per plpgsql function, not once
per expression.
setup_param_list() was allocating a fresh ParamListInfo for each query or
expression evaluation requested by a plpgsql function. There was probably
once good reason to do it like that, but for a long time we've had a
convention that there's a one-to-one mapping between the function's
PLpgSQL_datum array and the ParamListInfo slots, which means that a single
ParamListInfo can serve all the function's evaluation requests: the data
that would need to be passed is the same anyway.
In this patch, we retain the pattern of zeroing out the ParamListInfo
contents during each setup_param_list() call, because some of the slots may
be stale and we don't know exactly which ones. So this patch only saves a
palloc/pfree per evaluation cycle and nothing more; still, that seems to be
good for a couple percent overall speedup on simple-arithmetic type
statements. In future, though, we might be able to improve matters still
more by managing the param array contents more carefully.
Also, unify the former use of estate->cur_expr with that of
paramLI->parserSetupArg; they both were used to point to the active
expression, so we can combine the variables into just one.
---
src/pl/plpgsql/src/pl_exec.c | 91 +++++++++++++++++++-----------------
src/pl/plpgsql/src/plpgsql.h | 4 +-
2 files changed, 50 insertions(+), 45 deletions(-)
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index f24f55a2ff4..0ad32f72e9a 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -2197,10 +2197,6 @@ exec_stmt_forc(PLpgSQL_execstate *estate, PLpgSQL_stmt_forc *stmt)
elog(ERROR, "could not open cursor: %s",
SPI_result_code_string(SPI_result));
- /* don't need paramlist any more */
- if (paramLI)
- pfree(paramLI);
-
/*
* If cursor variable was NULL, store the generated portal name in it
*/
@@ -3169,6 +3165,16 @@ plpgsql_estate_setup(PLpgSQL_execstate *estate,
estate->datums = palloc(sizeof(PLpgSQL_datum *) * estate->ndatums);
/* caller is expected to fill the datums array */
+ /* initialize ParamListInfo with one entry per datum, all invalid */
+ estate->paramLI = (ParamListInfo)
+ palloc0(offsetof(ParamListInfoData, params) +
+ estate->ndatums * sizeof(ParamExternData));
+ estate->paramLI->paramFetch = plpgsql_param_fetch;
+ estate->paramLI->paramFetchArg = (void *) estate;
+ estate->paramLI->parserSetup = (ParserSetupHook) plpgsql_parser_setup;
+ estate->paramLI->parserSetupArg = NULL; /* filled during use */
+ estate->paramLI->numParams = estate->ndatums;
+
/* set up for use of appropriate simple-expression EState */
if (simple_eval_estate)
estate->simple_eval_estate = simple_eval_estate;
@@ -3179,7 +3185,6 @@ plpgsql_estate_setup(PLpgSQL_execstate *estate,
estate->eval_processed = 0;
estate->eval_lastoid = InvalidOid;
estate->eval_econtext = NULL;
- estate->cur_expr = NULL;
estate->err_stmt = NULL;
estate->err_text = NULL;
@@ -3495,9 +3500,6 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
(rc == SPI_OK_SELECT) ? errhint("If you want to discard the results of a SELECT, use PERFORM instead.") : 0));
}
- if (paramLI)
- pfree(paramLI);
-
return PLPGSQL_RC_OK;
}
@@ -3864,8 +3866,6 @@ exec_stmt_open(PLpgSQL_execstate *estate, PLpgSQL_stmt_open *stmt)
if (curname)
pfree(curname);
- if (paramLI)
- pfree(paramLI);
return PLPGSQL_RC_OK;
}
@@ -4050,7 +4050,7 @@ exec_assign_c_string(PLpgSQL_execstate *estate, PLpgSQL_datum *target,
/* ----------
- * exec_assign_value Put a value into a target field
+ * exec_assign_value Put a value into a target datum
*
* Note: in some code paths, this will leak memory in the eval_econtext;
* we assume that will be cleaned up later by exec_eval_cleanup. We cannot
@@ -4909,8 +4909,6 @@ exec_run_select(PLpgSQL_execstate *estate,
if (*portalP == NULL)
elog(ERROR, "could not open implicit cursor for query \"%s\": %s",
expr->query, SPI_result_code_string(SPI_result));
- if (paramLI)
- pfree(paramLI);
return SPI_OK_CURSOR;
}
@@ -4930,9 +4928,6 @@ exec_run_select(PLpgSQL_execstate *estate,
estate->eval_processed = SPI_processed;
estate->eval_lastoid = SPI_lastoid;
- if (paramLI)
- pfree(paramLI);
-
return rc;
}
@@ -5140,7 +5135,7 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
LocalTransactionId curlxid = MyProc->lxid;
CachedPlan *cplan;
ParamListInfo paramLI;
- PLpgSQL_expr *save_cur_expr;
+ void *save_setup_arg;
MemoryContext oldcontext;
/*
@@ -5216,14 +5211,10 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
}
/*
- * Create the param list in econtext's temporary memory context. We won't
- * need to free it explicitly, since it will go away at the next reset of
- * that context.
- *
- * Just for paranoia's sake, save and restore the prior value of
- * estate->cur_expr, which setup_param_list() sets.
+ * Set up param list. For safety, save and restore
+ * estate->paramLI->parserSetupArg around our use of the param list.
*/
- save_cur_expr = estate->cur_expr;
+ save_setup_arg = estate->paramLI->parserSetupArg;
paramLI = setup_param_list(estate, expr);
econtext->ecxt_param_list_info = paramLI;
@@ -5244,7 +5235,7 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
/* Assorted cleanup */
expr->expr_simple_in_use = false;
- estate->cur_expr = save_cur_expr;
+ estate->paramLI->parserSetupArg = save_setup_arg;
if (!estate->readonly_func)
PopActiveSnapshot();
@@ -5268,6 +5259,15 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
/*
* Create a ParamListInfo to pass to SPI
*
+ * We share a single ParamListInfo array across all SPI calls made from this
+ * estate. This is generally OK since any given slot in the array would
+ * need to contain the same current datum value no matter which query or
+ * expression we're evaluating. However, paramLI->parserSetupArg points to
+ * the specific PLpgSQL_expr being evaluated. This is not an issue for
+ * statement-level callers, but lower-level callers should save and restore
+ * estate->paramLI->parserSetupArg just in case there's an active evaluation
+ * at an outer call level.
+ *
* We fill in the values for any expression parameters that are plain
* PLpgSQL_var datums; these are cheap and safe to evaluate, and by setting
* them with PARAM_FLAG_CONST flags, we allow the planner to use those values
@@ -5277,9 +5277,6 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
* the expression that might never be evaluated at runtime. To handle those
* parameters, we set up a paramFetch hook for the executor to call when it
* wants a not-presupplied value.
- *
- * The result is a locally palloc'd array that should be pfree'd after use;
- * but note it can be NULL.
*/
static ParamListInfo
setup_param_list(PLpgSQL_execstate *estate, PLpgSQL_expr *expr)
@@ -5293,22 +5290,28 @@ setup_param_list(PLpgSQL_execstate *estate, PLpgSQL_expr *expr)
Assert(expr->plan != NULL);
/*
- * Could we re-use these arrays instead of palloc'ing a new one each time?
- * However, we'd have to re-fill the array each time anyway, since new
- * values might have been assigned to the variables.
+ * We only need a ParamListInfo if the expression has parameters. In
+ * principle we should test with bms_is_empty(), but we use a not-null
+ * test because it's faster. In current usage bits are never removed from
+ * expr->paramnos, only added, so this test is correct anyway.
*/
- if (!bms_is_empty(expr->paramnos))
+ if (expr->paramnos)
{
int dno;
- paramLI = (ParamListInfo)
- palloc0(offsetof(ParamListInfoData, params) +
- estate->ndatums * sizeof(ParamExternData));
- paramLI->paramFetch = plpgsql_param_fetch;
- paramLI->paramFetchArg = (void *) estate;
- paramLI->parserSetup = (ParserSetupHook) plpgsql_parser_setup;
- paramLI->parserSetupArg = (void *) expr;
- paramLI->numParams = estate->ndatums;
+ /* Use the common ParamListInfo for all evals in this estate */
+ paramLI = estate->paramLI;
+
+ /*
+ * Reset all entries to "invalid". It's pretty annoying to have to do
+ * this, but we don't currently track enough information to know which
+ * old entries might be obsolete. (There are a couple of nontrivial
+ * issues that would have to be dealt with in order to do better here.
+ * First, ROW and RECFIELD datums depend on other datums, and second,
+ * exec_eval_datum() will return short-lived palloc'd values for ROW
+ * and REC datums.)
+ */
+ MemSet(paramLI->params, 0, estate->ndatums * sizeof(ParamExternData));
/* Instantiate values for "safe" parameters of the expression */
dno = -1;
@@ -5330,10 +5333,10 @@ setup_param_list(PLpgSQL_execstate *estate, PLpgSQL_expr *expr)
/*
* Set up link to active expr where the hook functions can find it.
- * Callers must save and restore cur_expr if there is any chance that
- * they are interrupting an active use of parameters.
+ * Callers must save and restore parserSetupArg if there is any chance
+ * that they are interrupting an active use of parameters.
*/
- estate->cur_expr = expr;
+ paramLI->parserSetupArg = (void *) expr;
/*
* Also make sure this is set before parser hooks need it. There is
@@ -5373,7 +5376,7 @@ plpgsql_param_fetch(ParamListInfo params, int paramid)
/* fetch back the hook data */
estate = (PLpgSQL_execstate *) params->paramFetchArg;
- expr = estate->cur_expr;
+ expr = (PLpgSQL_expr *) params->parserSetupArg;
Assert(params->numParams == estate->ndatums);
/*
diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h
index 4ec462838f0..66d4da61d10 100644
--- a/src/pl/plpgsql/src/plpgsql.h
+++ b/src/pl/plpgsql/src/plpgsql.h
@@ -784,6 +784,9 @@ typedef struct PLpgSQL_execstate
int ndatums;
PLpgSQL_datum **datums;
+ /* we pass datums[i] to the executor, when needed, in paramLI->params[i] */
+ ParamListInfo paramLI;
+
/* EState to use for "simple" expression evaluation */
EState *simple_eval_estate;
@@ -792,7 +795,6 @@ typedef struct PLpgSQL_execstate
uint32 eval_processed;
Oid eval_lastoid;
ExprContext *eval_econtext; /* for executing simple expressions */
- PLpgSQL_expr *cur_expr; /* current query/expr being evaluated */
/* status information for error context reporting */
PLpgSQL_stmt *err_stmt; /* current stmt */
--
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