From fc79513062cfb877f3879cdb0006c33ab204caa6 Mon Sep 17 00:00:00 2001 From: "okbob@github.com" Date: Sat, 20 Jan 2024 08:56:17 +0100 Subject: [PATCH 15/18] plpgsql implementation for LET statement PLpgSQL allows to call expression executor directly (for simple expression). This possibility strongly reduces overhead related to execution. Reimplementation of LET statement (inside PLpgSQL) allows to use this possibility, and strongly increase performance: CREATE VARIABLE svar int; DO $$ BEGIN FOR i IN 1..10000 LOOP LET svar = i; END LOOP; END; $$; From 120ms to 8ms (with assertions) (this is best case, but without it, the LET statement can be bottle neck). An alternative can be reimplementation of LET statement inside expression executor, and then SQL LET command can be executed in simple expression execution, but this increase an complexity of executor, but still the benefits is only inside plpgsql, so it is better to this optimization inside plpgsql. --- src/backend/executor/spi.c | 3 ++ src/backend/parser/analyze.c | 12 ++++++ src/backend/parser/gram.y | 8 ++++ src/backend/parser/parser.c | 3 +- src/include/nodes/parsenodes.h | 2 + src/include/parser/parser.h | 4 ++ src/pl/plpgsql/src/pl_exec.c | 55 +++++++++++++++++++++++++ src/pl/plpgsql/src/pl_funcs.c | 24 +++++++++++ src/pl/plpgsql/src/pl_gram.y | 28 ++++++++++++- src/pl/plpgsql/src/pl_reserved_kwlist.h | 1 + src/pl/plpgsql/src/plpgsql.h | 12 ++++++ src/tools/pgindent/typedefs.list | 1 + 12 files changed, 151 insertions(+), 2 deletions(-) diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c index d71484c0b8..f98d06d569 100644 --- a/src/backend/executor/spi.c +++ b/src/backend/executor/spi.c @@ -2967,6 +2967,9 @@ _SPI_error_callback(void *arg) case RAW_PARSE_PLPGSQL_ASSIGN3: errcontext("PL/pgSQL assignment \"%s\"", query); break; + case RAW_PARSE_PLPGSQL_LET: + errcontext("LET statement \"%s\"", query); + break; default: errcontext("SQL statement \"%s\"", query); break; diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c index 70b040322f..52e9871e43 100644 --- a/src/backend/parser/analyze.c +++ b/src/backend/parser/analyze.c @@ -1921,6 +1921,18 @@ transformLetStmt(ParseState *pstate, LetStmt *stmt) stmt->query = (Node *) query; + /* + * Inside PL/pgSQL we don't want to execute LET statement as utility + * command, because it disallow to execute expression as simple + * expression. So for PL/pgSQL we have extra path, and we return SELECT. + * Then it can be executed by exec_eval_expr. Result is dirrectly assigned + * to target session variable inside PL/pgSQL LET statement handler. This + * is extra code, extra path, but possibility to get faster execution is + * too attractive. + */ + if (stmt->plpgsql_mode) + return query; + /* represent the command as a utility Query */ result = makeNode(Query); result->commandType = CMD_UTILITY; diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y index 05bf116222..6223887b26 100644 --- a/src/backend/parser/gram.y +++ b/src/backend/parser/gram.y @@ -813,6 +813,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query); %token MODE_PLPGSQL_ASSIGN1 %token MODE_PLPGSQL_ASSIGN2 %token MODE_PLPGSQL_ASSIGN3 +%token MODE_PLPGSQL_LET /* Precedence: lowest to highest */ @@ -941,6 +942,13 @@ parse_toplevel: pg_yyget_extra(yyscanner)->parsetree = list_make1(makeRawStmt((Node *) n, 0)); } + | MODE_PLPGSQL_LET LetStmt + { + LetStmt *n = (LetStmt *) $2; + n->plpgsql_mode = true; + pg_yyget_extra(yyscanner)->parsetree = + list_make1(makeRawStmt((Node *) n, 0)); + } ; /* diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c index 9ec628ecbd..f4397f380f 100644 --- a/src/backend/parser/parser.c +++ b/src/backend/parser/parser.c @@ -61,7 +61,8 @@ raw_parser(const char *str, RawParseMode mode) MODE_PLPGSQL_EXPR, /* RAW_PARSE_PLPGSQL_EXPR */ MODE_PLPGSQL_ASSIGN1, /* RAW_PARSE_PLPGSQL_ASSIGN1 */ MODE_PLPGSQL_ASSIGN2, /* RAW_PARSE_PLPGSQL_ASSIGN2 */ - MODE_PLPGSQL_ASSIGN3 /* RAW_PARSE_PLPGSQL_ASSIGN3 */ + MODE_PLPGSQL_ASSIGN3, /* RAW_PARSE_PLPGSQL_ASSIGN3 */ + MODE_PLPGSQL_LET /* RAW_PARSE_PLPGSQL_LET */ }; yyextra.have_lookahead = true; diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h index db178d44b5..04f804bdf6 100644 --- a/src/include/nodes/parsenodes.h +++ b/src/include/nodes/parsenodes.h @@ -1944,6 +1944,8 @@ typedef struct LetStmt NodeTag type; List *target; /* target variable */ Node *query; /* source expression */ + bool plpgsql_mode; /* true, when command will be executed + * (parsed) by plpgsql runtime */ int location; } LetStmt; diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h index be184ec506..efbc76f0ad 100644 --- a/src/include/parser/parser.h +++ b/src/include/parser/parser.h @@ -33,6 +33,9 @@ * RAW_PARSE_PLPGSQL_ASSIGNn: parse a PL/pgSQL assignment statement, * and return a one-element List containing a RawStmt node. "n" * gives the number of dotted names comprising the target ColumnRef. + * + * RAW_PARSE_PLPGSQL_LET: parse a LET statement, and return a + * one-element List containing a RawStmt node. */ typedef enum { @@ -42,6 +45,7 @@ typedef enum RAW_PARSE_PLPGSQL_ASSIGN1, RAW_PARSE_PLPGSQL_ASSIGN2, RAW_PARSE_PLPGSQL_ASSIGN3, + RAW_PARSE_PLPGSQL_LET, } RawParseMode; /* Values for the backslash_quote GUC */ diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c index 6d1691340c..aaa9a6bb0a 100644 --- a/src/pl/plpgsql/src/pl_exec.c +++ b/src/pl/plpgsql/src/pl_exec.c @@ -24,6 +24,7 @@ #include "catalog/pg_proc.h" #include "catalog/pg_type.h" #include "commands/defrem.h" +#include "commands/session_variable.h" #include "executor/execExpr.h" #include "executor/spi.h" #include "executor/tstoreReceiver.h" @@ -328,6 +329,8 @@ static int exec_stmt_commit(PLpgSQL_execstate *estate, PLpgSQL_stmt_commit *stmt); static int exec_stmt_rollback(PLpgSQL_execstate *estate, PLpgSQL_stmt_rollback *stmt); +static int exec_stmt_let(PLpgSQL_execstate *estate, + PLpgSQL_stmt_let *let); static void plpgsql_estate_setup(PLpgSQL_execstate *estate, PLpgSQL_function *func, @@ -2119,6 +2122,10 @@ exec_stmts(PLpgSQL_execstate *estate, List *stmts) rc = exec_stmt_rollback(estate, (PLpgSQL_stmt_rollback *) stmt); break; + case PLPGSQL_STMT_LET: + rc = exec_stmt_let(estate, (PLpgSQL_stmt_let *) stmt); + break; + default: /* point err_stmt to parent, since this one seems corrupt */ estate->err_stmt = save_estmt; @@ -4998,6 +5005,54 @@ exec_stmt_rollback(PLpgSQL_execstate *estate, PLpgSQL_stmt_rollback *stmt) return PLPGSQL_RC_OK; } +/* ---------- + * exec_stmt_let Evaluate an expression and + * put the result into a session variable. + * ---------- + */ +static int +exec_stmt_let(PLpgSQL_execstate *estate, PLpgSQL_stmt_let *stmt) +{ + bool isNull; + Oid valtype; + int32 valtypmod; + Datum value; + Oid varid; + + List *plansources; + CachedPlanSource *plansource; + + value = exec_eval_expr(estate, + stmt->expr, + &isNull, + &valtype, + &valtypmod); + + /* + * Oid of target session variable is stored in Query structure. It is + * safer to read this value directly from the plan than to hold this value + * in the plpgsql context, because it's not necessary to handle + * invalidation of the cached value. Next operations are read only without + * any allocations, so we can expect that retrieving varid from Query + * should be fast. + */ + plansources = SPI_plan_get_plan_sources(stmt->expr->plan); + if (list_length(plansources) != 1) + elog(ERROR, "unexpected length of plansources of query for LET statement"); + + plansource = (CachedPlanSource *) linitial(plansources); + if (list_length(plansource->query_list) != 1) + elog(ERROR, "unexpected length of plansource of query for LET statement"); + + varid = linitial_node(Query, plansource->query_list)->resultVariable; + if (!OidIsValid(varid)) + elog(ERROR, "oid of target session variable is not valid"); + + SetSessionVariableWithSecurityCheck(varid, value, isNull); + + return PLPGSQL_RC_OK; +} + /* ---------- * exec_assign_expr Put an expression's result into a variable. * ---------- diff --git a/src/pl/plpgsql/src/pl_funcs.c b/src/pl/plpgsql/src/pl_funcs.c index eeb7c4d7c0..1b39351db7 100644 --- a/src/pl/plpgsql/src/pl_funcs.c +++ b/src/pl/plpgsql/src/pl_funcs.c @@ -288,6 +288,8 @@ plpgsql_stmt_typename(PLpgSQL_stmt *stmt) return "COMMIT"; case PLPGSQL_STMT_ROLLBACK: return "ROLLBACK"; + case PLPGSQL_STMT_LET: + return "LET"; } return "unknown"; @@ -370,6 +372,7 @@ static void free_perform(PLpgSQL_stmt_perform *stmt); static void free_call(PLpgSQL_stmt_call *stmt); static void free_commit(PLpgSQL_stmt_commit *stmt); static void free_rollback(PLpgSQL_stmt_rollback *stmt); +static void free_let(PLpgSQL_stmt_let *stmt); static void free_expr(PLpgSQL_expr *expr); @@ -459,6 +462,9 @@ free_stmt(PLpgSQL_stmt *stmt) case PLPGSQL_STMT_ROLLBACK: free_rollback((PLpgSQL_stmt_rollback *) stmt); break; + case PLPGSQL_STMT_LET: + free_let((PLpgSQL_stmt_let *) stmt); + break; default: elog(ERROR, "unrecognized cmd_type: %d", stmt->cmd_type); break; @@ -713,6 +719,12 @@ free_getdiag(PLpgSQL_stmt_getdiag *stmt) { } +static void +free_let(PLpgSQL_stmt_let *stmt) +{ + free_expr(stmt->expr); +} + static void free_expr(PLpgSQL_expr *expr) { @@ -815,6 +827,7 @@ static void dump_perform(PLpgSQL_stmt_perform *stmt); static void dump_call(PLpgSQL_stmt_call *stmt); static void dump_commit(PLpgSQL_stmt_commit *stmt); static void dump_rollback(PLpgSQL_stmt_rollback *stmt); +static void dump_let(PLpgSQL_stmt_let *stmt); static void dump_expr(PLpgSQL_expr *expr); @@ -914,6 +927,9 @@ dump_stmt(PLpgSQL_stmt *stmt) case PLPGSQL_STMT_ROLLBACK: dump_rollback((PLpgSQL_stmt_rollback *) stmt); break; + case PLPGSQL_STMT_LET: + dump_let((PLpgSQL_stmt_let *) stmt); + break; default: elog(ERROR, "unrecognized cmd_type: %d", stmt->cmd_type); break; @@ -1590,6 +1606,14 @@ dump_getdiag(PLpgSQL_stmt_getdiag *stmt) printf("\n"); } +static void +dump_let(PLpgSQL_stmt_let *stmt) +{ + dump_ind(); + dump_expr(stmt->expr); + printf("\n"); +} + static void dump_expr(PLpgSQL_expr *expr) { diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y index e630498e82..eb861dd36f 100644 --- a/src/pl/plpgsql/src/pl_gram.y +++ b/src/pl/plpgsql/src/pl_gram.y @@ -196,7 +196,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt); %type stmt_return stmt_raise stmt_assert stmt_execsql %type stmt_dynexecute stmt_for stmt_perform stmt_call stmt_getdiag %type stmt_open stmt_fetch stmt_move stmt_close stmt_null -%type stmt_commit stmt_rollback +%type stmt_commit stmt_rollback stmt_let %type stmt_case stmt_foreach_a %type proc_exceptions @@ -303,6 +303,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt); %token K_INTO %token K_IS %token K_LAST +%token K_LET %token K_LOG %token K_LOOP %token K_MERGE @@ -872,6 +873,8 @@ proc_stmt : pl_block ';' { $$ = $1; } | stmt_rollback { $$ = $1; } + | stmt_let + { $$ = $1; } ; stmt_perform : K_PERFORM @@ -988,6 +991,29 @@ stmt_assign : T_DATUM } ; +stmt_let : K_LET + { + PLpgSQL_stmt_let *new; + RawParseMode pmode; + + pmode = RAW_PARSE_PLPGSQL_LET; + + new = palloc0(sizeof(PLpgSQL_stmt_let)); + new->cmd_type = PLPGSQL_STMT_LET; + new->lineno = plpgsql_location_to_lineno(@1); + new->stmtid = ++plpgsql_curr_compile->nstatements; + + /* Push back the head name to include it in the stmt */ + plpgsql_push_back_token(K_LET); + new->expr = read_sql_construct(';', 0, 0, ";", + pmode, + false, true, true, + NULL, NULL); + + $$ = (PLpgSQL_stmt *)new; + } + ; + stmt_getdiag : K_GET getdiag_area_opt K_DIAGNOSTICS getdiag_list ';' { PLpgSQL_stmt_getdiag *new; diff --git a/src/pl/plpgsql/src/pl_reserved_kwlist.h b/src/pl/plpgsql/src/pl_reserved_kwlist.h index d338e9f637..be94aa751a 100644 --- a/src/pl/plpgsql/src/pl_reserved_kwlist.h +++ b/src/pl/plpgsql/src/pl_reserved_kwlist.h @@ -40,6 +40,7 @@ PG_KEYWORD("from", K_FROM) PG_KEYWORD("if", K_IF) PG_KEYWORD("in", K_IN) PG_KEYWORD("into", K_INTO) +PG_KEYWORD("let", K_LET) PG_KEYWORD("loop", K_LOOP) PG_KEYWORD("not", K_NOT) PG_KEYWORD("null", K_NULL) diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h index 40056bb851..0b5cd091ff 100644 --- a/src/pl/plpgsql/src/plpgsql.h +++ b/src/pl/plpgsql/src/plpgsql.h @@ -128,6 +128,7 @@ typedef enum PLpgSQL_stmt_type PLPGSQL_STMT_CALL, PLPGSQL_STMT_COMMIT, PLPGSQL_STMT_ROLLBACK, + PLPGSQL_STMT_LET, } PLpgSQL_stmt_type; /* @@ -520,6 +521,17 @@ typedef struct PLpgSQL_stmt_assign PLpgSQL_expr *expr; } PLpgSQL_stmt_assign; +/* + * Let statement + */ +typedef struct PLpgSQL_stmt_let +{ + PLpgSQL_stmt_type cmd_type; + int lineno; + unsigned int stmtid; + PLpgSQL_expr *expr; +} PLpgSQL_stmt_let; + /* * PERFORM statement */ diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 393c8c5850..404b51f408 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -1820,6 +1820,7 @@ PLpgSQL_stmt_forq PLpgSQL_stmt_fors PLpgSQL_stmt_getdiag PLpgSQL_stmt_if +PLpgSQL_stmt_let PLpgSQL_stmt_loop PLpgSQL_stmt_open PLpgSQL_stmt_perform -- 2.43.0