On Wed, Jul 18, 2018 at 08:25:46AM -0400, Fabien COELHO wrote: > > Hello David, > > >I assure you that you expression yourself in English a good deal > >better than I do in Portuguese. > > Alas, despite a Portuguese "rabbit" name, I cannot speak the language which > got lost between generations.
I fear my kids may lose French the same way. Mine's already not great, and that's in just one generation. > About this v3: Patch applies, compiles, "make check" ok. > > A few minor comments: > > Variable "need_transform_null_equals" may be better named "is_null_equals", > because there is no "need" of the transformation as such, and the expression > just checks for the pattern, really. Done. > I'm fine with the off/warn/error/on order. > > Doc could mention that the transformation allows compatibility with other > products, without naming them? Or not. I don't see a point in obscuring the origin. > In doc, the list of valid values on a long line, where the practice seems to > wrap around after about 80 columns in the XML file. Fixed. > I notice that the feature was not tested at all before this patch:-( > > Maybe there could be one test which results to true, which is the whole > point of the transformation? eg "SELECT NULL = NULL". Done. Best, David. -- David Fetter <david(at)fetter(dot)org> http://fetter.org/ Phone: +1 415 235 3778 Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate
>From 1c0d16c79dba628ec10fd1554574cf497b3dfffb Mon Sep 17 00:00:00 2001 From: David Fetter <da...@fetter.org> Date: Sun, 15 Jul 2018 16:11:08 -0700 Subject: [PATCH] Make transform_null_equals into an enum v4 MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="------------2.17.1" This is a multi-part message in MIME format. --------------2.17.1 Content-Type: text/plain; charset=UTF-8; format=fixed Content-Transfer-Encoding: 8bit The transform_null_equals GUC can now be off, warn, error, or on. --- doc/src/sgml/config.sgml | 25 ++++++--- src/backend/parser/parse_expr.c | 30 ++++++++-- src/backend/utils/misc/guc.c | 44 ++++++++++----- src/backend/utils/misc/postgresql.conf.sample | 2 +- src/include/parser/parse_expr.h | 11 +++- src/test/regress/expected/guc.out | 55 +++++++++++++++++++ src/test/regress/sql/guc.sql | 26 +++++++++ 7 files changed, 164 insertions(+), 29 deletions(-) --------------2.17.1 Content-Type: text/x-patch; name="0001-Make-transform_null_equals-into-an-enum-v4.patch" Content-Transfer-Encoding: 8bit Content-Disposition: attachment; filename="0001-Make-transform_null_equals-into-an-enum-v4.patch" diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 4d48d93305..6468c2253f 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -8066,7 +8066,7 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir' <variablelist> <varlistentry id="guc-transform-null-equals" xreflabel="transform_null_equals"> - <term><varname>transform_null_equals</varname> (<type>boolean</type>) + <term><varname>transform_null_equals</varname> (<type>enum</type>) <indexterm><primary>IS NULL</primary></indexterm> <indexterm> <primary><varname>transform_null_equals</varname> configuration parameter</primary> @@ -8074,15 +8074,24 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir' </term> <listitem> <para> - When on, expressions of the form <literal><replaceable>expr</replaceable> = - NULL</literal> (or <literal>NULL = - <replaceable>expr</replaceable></literal>) are treated as + When enabled, expressions of the form + <literal><replaceable>expr</replaceable> = NULL</literal> (or + <literal>NULL = <replaceable>expr</replaceable></literal>) are treated as <literal><replaceable>expr</replaceable> IS NULL</literal>, that is, they return true if <replaceable>expr</replaceable> evaluates to the null value, - and false otherwise. The correct SQL-spec-compliant behavior of - <literal><replaceable>expr</replaceable> = NULL</literal> is to always - return null (unknown). Therefore this parameter defaults to - <literal>off</literal>. + and false otherwise. Valid values are <literal>off</literal>, + <literal>warn</literal>, <literal>error</literal>, and <literal>on</literal>. + </para> + + <para> + The correct SQL-spec-compliant behavior of + <literal><replaceable>expr</replaceable> = <replacable>null_expression</replaceable></literal> + is to always return null (unknown); PostgreSQL allows <literal>NULL</literal> + as a null-valued expression of unknown type, which is an extension to the spec. + The transformation of <literal><replaceable>expr</replaceable> = NULL</literal> + to <literal><replaceable>expr</replaceable> IS NULL</literal> is inconsistent + with the normal semantics of the SQL specification, and is therefore set to "off" + by default. </para> <para> diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c index 385e54a9b6..53970a8ce6 100644 --- a/src/backend/parser/parse_expr.c +++ b/src/backend/parser/parse_expr.c @@ -41,8 +41,8 @@ /* GUC parameters */ -bool operator_precedence_warning = false; -bool Transform_null_equals = false; +bool operator_precedence_warning = false; +enum TransformNullEquals transform_null_equals = TRANSFORM_NULL_EQUALS_OFF; /* * Node-type groups for operator precedence warnings @@ -850,6 +850,7 @@ transformAExprOp(ParseState *pstate, A_Expr *a) Node *lexpr = a->lexpr; Node *rexpr = a->rexpr; Node *result; + bool is_null_equals = false; if (operator_precedence_warning) { @@ -872,17 +873,34 @@ transformAExprOp(ParseState *pstate, A_Expr *a) } /* - * Special-case "foo = NULL" and "NULL = foo" for compatibility with + * Deal with "foo = NULL" and "NULL = foo" for compatibility with * standards-broken products (like Microsoft's). Turn these into IS NULL * exprs. (If either side is a CaseTestExpr, then the expression was * generated internally from a CASE-WHEN expression, and * transform_null_equals does not apply.) */ - if (Transform_null_equals && - list_length(a->name) == 1 && + is_null_equals = (list_length(a->name) == 1 && strcmp(strVal(linitial(a->name)), "=") == 0 && (exprIsNullConstant(lexpr) || exprIsNullConstant(rexpr)) && - (!IsA(lexpr, CaseTestExpr) &&!IsA(rexpr, CaseTestExpr))) + (!IsA(lexpr, CaseTestExpr) &&!IsA(rexpr, CaseTestExpr))); + + /* + * We don't need to handle TRANSFORM_NULL_EQUALS_OFF here because it's a noop + */ + + if (is_null_equals && transform_null_equals == TRANSFORM_NULL_EQUALS_WARN) + ereport(WARNING, + (errcode(ERRCODE_WRONG_OBJECT_TYPE), + errmsg("= NULL can only produce a NULL"), + parser_errposition(pstate, a->location))); + + if (is_null_equals && transform_null_equals == TRANSFORM_NULL_EQUALS_ERR) + ereport(ERROR, + (errcode(ERRCODE_WRONG_OBJECT_TYPE), + errmsg("= NULL does not comply with the SQL specification"), + parser_errposition(pstate, a->location))); + + if (is_null_equals && transform_null_equals == TRANSFORM_NULL_EQUALS_ON) { NullTest *n = makeNode(NullTest); diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index a88ea6cfc9..d441bccb10 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -310,6 +310,23 @@ static const struct config_enum_entry track_function_options[] = { {NULL, 0, false} }; +/* + * Accept the usual variants of boolean-ish, along with warn and error. + */ +static const struct config_enum_entry transform_null_equals_options[] = { + {"off", TRANSFORM_NULL_EQUALS_OFF, false}, + {"false", TRANSFORM_NULL_EQUALS_OFF, true}, + {"no", TRANSFORM_NULL_EQUALS_OFF, true}, + {"0", TRANSFORM_NULL_EQUALS_OFF, true}, + {"warn", TRANSFORM_NULL_EQUALS_WARN, false}, + {"error", TRANSFORM_NULL_EQUALS_ERR, false}, + {"on", TRANSFORM_NULL_EQUALS_ON, false}, + {"true", TRANSFORM_NULL_EQUALS_ON, true}, + {"yes", TRANSFORM_NULL_EQUALS_ON, true}, + {"1", TRANSFORM_NULL_EQUALS_ON, true}, + {NULL, 0, false} +}; + static const struct config_enum_entry xmlbinary_options[] = { {"base64", XMLBINARY_BASE64, false}, {"hex", XMLBINARY_HEX, false}, @@ -1414,19 +1431,6 @@ static struct config_bool ConfigureNamesBool[] = false, NULL, NULL, NULL }, - { - {"transform_null_equals", PGC_USERSET, COMPAT_OPTIONS_CLIENT, - gettext_noop("Treats \"expr=NULL\" as \"expr IS NULL\"."), - gettext_noop("When turned on, expressions of the form expr = NULL " - "(or NULL = expr) are treated as expr IS NULL, that is, they " - "return true if expr evaluates to the null value, and false " - "otherwise. The correct behavior of expr = NULL is to always " - "return null (unknown).") - }, - &Transform_null_equals, - false, - NULL, NULL, NULL - }, { {"db_user_namespace", PGC_SIGHUP, CONN_AUTH_AUTH, gettext_noop("Enables per-database user names."), @@ -4074,6 +4078,20 @@ static struct config_enum ConfigureNamesEnum[] = NULL, NULL, NULL }, + { + {"transform_null_equals", PGC_USERSET, COMPAT_OPTIONS_CLIENT, + gettext_noop("Treats \"expr=NULL\" as \"expr IS NULL\"."), + gettext_noop("When set to on, expressions of the form expr = NULL " + "(or NULL = expr) are treated as expr IS NULL. When " + "set to off, warn, or error, they are not, with increasing " + "insistence. The default behavior of expr = NULL is to " + "return null (unknown).") + }, + &transform_null_equals, + TRANSFORM_NULL_EQUALS_OFF, transform_null_equals_options, + NULL, NULL, NULL + }, + { {"wal_level", PGC_POSTMASTER, WAL_SETTINGS, gettext_noop("Set the level of information written to the WAL."), diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index c0d3fb8491..07dda7b746 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -656,7 +656,7 @@ # - Other Platforms and Clients - -#transform_null_equals = off +#transform_null_equals = off # off, warn, error, or on #------------------------------------------------------------------------------ diff --git a/src/include/parser/parse_expr.h b/src/include/parser/parse_expr.h index e5aff61b8f..2f3dc28858 100644 --- a/src/include/parser/parse_expr.h +++ b/src/include/parser/parse_expr.h @@ -17,10 +17,19 @@ /* GUC parameters */ extern bool operator_precedence_warning; -extern bool Transform_null_equals; extern Node *transformExpr(ParseState *pstate, Node *expr, ParseExprKind exprKind); extern const char *ParseExprKindName(ParseExprKind exprKind); +typedef enum TransformNullEquals +{ + TRANSFORM_NULL_EQUALS_OFF = 0, /* Disabled */ + TRANSFORM_NULL_EQUALS_WARN, /* Issue a warning */ + TRANSFORM_NULL_EQUALS_ERR, /* Error out */ + TRANSFORM_NULL_EQUALS_ON /* Enabled */ +} TransformNullEquals; + +extern TransformNullEquals transform_null_equals; + #endif /* PARSE_EXPR_H */ diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out index 43ac5f5f11..cc4fdf2de8 100644 --- a/src/test/regress/expected/guc.out +++ b/src/test/regress/expected/guc.out @@ -767,3 +767,58 @@ NOTICE: text search configuration "no_such_config" does not exist select func_with_bad_set(); ERROR: invalid value for parameter "default_text_search_config": "no_such_config" reset check_function_bodies; +set transform_null_equals = off; +select 1=null as transform_null_equals_off; + transform_null_equals_off +--------------------------- + +(1 row) + +select null=null as transform_null_equals_off; + transform_null_equals_off +--------------------------- + +(1 row) + +set transform_null_equals = warn; +select 1=null as transform_null_equals_warn; +WARNING: = NULL can only produce a NULL +LINE 1: select 1=null as transform_null_equals_warn; + ^ + transform_null_equals_warn +---------------------------- + +(1 row) + +select null=null as transform_null_equals_warn; +WARNING: = NULL can only produce a NULL +LINE 1: select null=null as transform_null_equals_warn; + ^ + transform_null_equals_warn +---------------------------- + +(1 row) + +set transform_null_equals = error; +select 1=null as transform_null_equals_error; +ERROR: = NULL does not comply with the SQL specification +LINE 1: select 1=null as transform_null_equals_error; + ^ +select null=null as transform_null_equals_error; +ERROR: = NULL does not comply with the SQL specification +LINE 1: select null=null as transform_null_equals_error; + ^ +set transform_null_equals = on; +select 1=null as transform_null_equals_on; + transform_null_equals_on +-------------------------- + f +(1 row) + +select null=null as transform_null_equals_on; + transform_null_equals_on +-------------------------- + t +(1 row) + +reset transform_null_equals; diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql index 23e5029780..24fa8c5308 100644 --- a/src/test/regress/sql/guc.sql +++ b/src/test/regress/sql/guc.sql @@ -288,3 +288,29 @@ set default_text_search_config = no_such_config; select func_with_bad_set(); reset check_function_bodies; + +set transform_null_equals = off; + +select 1=null as transform_null_equals_off; + +select null=null as transform_null_equals_off; + +set transform_null_equals = warn; + +select 1=null as transform_null_equals_warn; + +select null=null as transform_null_equals_warn; + +set transform_null_equals = error; + +select 1=null as transform_null_equals_error; + +select null=null as transform_null_equals_error; + +set transform_null_equals = on; + +select 1=null as transform_null_equals_on; + +select null=null as transform_null_equals_on; + +reset transform_null_equals; --------------2.17.1--