From 3be9e8866fb7a6634f27b85eb0bcbcbf8357fbe4 Mon Sep 17 00:00:00 2001 From: Abhijit Menon-Sen Date: Sun, 27 Sep 2020 17:00:53 +0530 Subject: Support SET +=/-= syntax for numeric configuration settings This allows SET to modify the value of PGC_INT and PGC_REAL settings with the += and -= operations introduced earlier, by adding/subtracting the argument (which may be an integer, a real, or a string representing one of those two with some appropriate unit). Examples: SET cpu_tuple_cost += 0.01; SET effective_cache_size += '2GB'; ALTER SYSTEM SET max_worker_processes += 4; --- doc/src/sgml/ref/set.sgml | 6 ++ src/backend/utils/misc/guc.c | 114 ++++++++++++++++++++++++++++++++++- 2 files changed, 118 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/ref/set.sgml b/doc/src/sgml/ref/set.sgml index e30e9b42f0..4da3e05396 100644 --- a/doc/src/sgml/ref/set.sgml +++ b/doc/src/sgml/ref/set.sgml @@ -49,6 +49,12 @@ SET [ SESSION | LOCAL ] TIME ZONE { timezone + + You can also use += and -= to change + numeric configuration parameters, such as cpu_tuple_cost + or effective_cache_size. + + If SET (or equivalently SET SESSION) is issued within a transaction that is later aborted, the effects of the diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 9e56f64fec..f8e74d8991 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -7986,6 +7986,108 @@ flatten_set_variable_args(const char *name, List *args) return buf.data; } +/* + * alter_set_number_args + * Given a parsenode List as emitted by the grammar for SET, + * convert to the flat string representation used by GUC, with the + * args added to or subtracted from the current numeric (integer or + * real) value of the setting, depending on the desired operation + * + * The result is a palloc'd string. + */ +static char * +alter_set_number_args(struct config_generic *record, VariableSetKind operation, + List *args) +{ + StringInfoData value; + Node *arg = (Node *) linitial(args); + NodeTag tag; + A_Const *con; + + if (!IsA(arg, A_Const)) + elog(ERROR, "unrecognized node type: %d", (int) nodeTag(arg)); + + con = (A_Const *) arg; + tag = nodeTag(&con->val); + + /* + * The single constant argument may be an integer, a floating point + * value, or a string representing one of those two things. Once we + * have the desired change (positive or negative), we can just add + * it to the current value. + */ + if (record->vartype == PGC_INT) + { + struct config_int *conf = (struct config_int *) record; + int64 current = *conf->variable; + int delta = 0; + + if (tag == T_Integer) + delta = intVal(&con->val); + else if (tag == T_String) + { + const char *value = strVal(&con->val); + const char *hintmsg; + + if (!parse_int(value, &delta, conf->gen.flags, &hintmsg)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("invalid value for parameter \"%s\": \"%s\"", + record->name, value), + hintmsg ? errhint("%s", _(hintmsg)) : 0)); + } + else + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("invalid value for parameter \"%s\"", + record->name))); + + delta = operation == VAR_ADD_VALUE ? delta : -delta; + if ((delta > 0 && current < PG_INT64_MAX - delta) + || (delta < 0 && current > PG_INT64_MIN - delta)) + current = current + delta; + + initStringInfo(&value); + appendStringInfo(&value, INT64_FORMAT, current); + } + else if (record->vartype == PGC_REAL) + { + struct config_real *conf = (struct config_real *) record; + double current = *conf->variable; + double delta = 0; + + if (tag == T_Float) + delta = floatVal(&con->val); + else if (tag == T_Integer) + delta = intVal(&con->val); + else if (tag == T_String) + { + const char *value = strVal(&con->val); + const char *hintmsg; + + if (!parse_real(value, &delta, conf->gen.flags, &hintmsg)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("invalid value for parameter \"%s\": \"%s\"", + record->name, value), + hintmsg ? errhint("%s", _(hintmsg)) : 0)); + } + else + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("invalid value for parameter \"%s\"", + record->name))); + + delta = operation == VAR_ADD_VALUE ? delta : -delta; + current = current + delta; + + initStringInfo(&value); + appendStringInfo(&value, "%g", current); + } + + return value.data; +} + /* * alter_set_variable_args * Given a parsenode List as emitted by the grammar for SET, @@ -8016,8 +8118,16 @@ alter_set_variable_args(const char *name, VariableSetKind operation, List *args) errmsg("unrecognized configuration parameter \"%s\"", name))); /* - * At present, this function can operate only on a list represented - * as a comma-separated string. + * If the setting is a number and there's only one argument, we deal + * with it separately. + */ + if ((record->vartype == PGC_INT || record->vartype == PGC_REAL) + && list_length(args) == 1) + return alter_set_number_args(record, operation, args); + + /* + * This function can operate only on a list represented as a + * comma-separated string. */ if (record->vartype != PGC_STRING || (record->flags & GUC_LIST_INPUT) == 0) ereport(ERROR, -- 2.27.0