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Changed insert/update of GENERATED fields

Changed the way GENERATED fields are inserted/updated. Previously we
used the DEFAULT keyword for INSERTing; now, we expose the generating
expression to the user, but ommit the field when inserting or updating a
feature.
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espinafre authored and nyalldawson committed May 25, 2020
1 parent a6208da commit e16ece75414cdbec34ae13853df0362b9127b1f3
@@ -920,7 +920,7 @@ bool QgsPostgresProvider::loadFields()
notNullMap[attrelid][attnum] = attNotNull;
uniqueMap[attrelid][attnum] = uniqueConstraint;
identityMap[attrelid][attnum] = attIdentity.isEmpty() ? " " : attIdentity;
generatedMap[attrelid][attnum] = attGenerated;
generatedMap[attrelid][attnum] = attGenerated == "s" ? defVal : "";
}
}
}
@@ -2081,10 +2081,14 @@ QString QgsPostgresProvider::defaultValueClause( int fieldId ) const

// with generated columns (PostgreSQL 12+), the provider will ALWAYS evaluate the default values.
// The only acceptable value for such columns on INSERT or UPDATE clauses is the keyword "DEFAULT".
// Here, we return the expression used to generate the field value, so the
// user can see what is happening when inserting a new feature.
// On inserting a new feature or updating a generated field, this is
// ommited from the generated queries.
// See https://www.postgresql.org/docs/12/ddl-generated-columns.html
if ( !genVal.isEmpty() )
{
return "DEFAULT";
return defVal;
}

if ( !providerProperty( EvaluateDefaultValues, false ).toBool() && !defVal.isEmpty() )
@@ -2338,6 +2342,13 @@ bool QgsPostgresProvider::addFeatures( QgsFeatureList &flist, Flags flags )
continue;

QString fieldname = mAttributeFields.at( idx ).name();

if ( mGeneratedValues.contains( idx ) && !mGeneratedValues.value( idx, QString() ).isEmpty() )
{
QgsDebugMsg( QStringLiteral( "Skipping field %1 (idx %2) which is GENERATED." ).arg( fieldname, idx ) );
continue;
}

QString fieldTypeName = mAttributeFields.at( idx ).typeName();

QgsDebugMsgLevel( "Checking field against: " + fieldname, 2 );
@@ -2941,6 +2952,7 @@ bool QgsPostgresProvider::changeAttributeValues( const QgsChangedAttributesMap &

// cycle through the changed attributes of the feature
QString delim;
int numChangedFields = 0;
for ( QgsAttributeMap::const_iterator siter = attrs.constBegin(); siter != attrs.constEnd(); ++siter )
{
try
@@ -2949,6 +2961,14 @@ bool QgsPostgresProvider::changeAttributeValues( const QgsChangedAttributesMap &

pkChanged = pkChanged || mPrimaryKeyAttrs.contains( siter.key() );

if ( mGeneratedValues.contains( siter.key() ) && !mGeneratedValues.value( siter.key(), QString() ).isEmpty() )
{
pushError( tr( "Changing the value of GENERATED field %1 is not allowed." ).arg( fld.name() ) );
continue;
}

numChangedFields++;

sql += delim + QStringLiteral( "%1=" ).arg( quotedIdentifier( fld.name() ) );
delim = ',';

@@ -2990,9 +3010,14 @@ bool QgsPostgresProvider::changeAttributeValues( const QgsChangedAttributesMap &

sql += QStringLiteral( " WHERE %1" ).arg( whereClause( fid ) );

QgsPostgresResult result( conn->PQexec( sql ) );
if ( result.PQresultStatus() != PGRES_COMMAND_OK && result.PQresultStatus() != PGRES_TUPLES_OK )
throw PGException( result );
// Don't try to UPDATE an empty set of values (might happen if the table only has GENERATED fields,
// or if the user only changed GENERATED fields in the form/attribute table.
if ( numChangedFields > 0 )
{
QgsPostgresResult result( conn->PQexec( sql ) );
if ( result.PQresultStatus() != PGRES_COMMAND_OK && result.PQresultStatus() != PGRES_TUPLES_OK )
throw PGException( result );
}

// update feature id map if key was changed
if ( pkChanged && mPrimaryKeyType == PktFidMap )
@@ -3,6 +3,7 @@

CREATE TABLE qgis_test.test_gen_col (
id SERIAL PRIMARY KEY,
name varchar(32),
geom GEOMETRY('Polygon', 4326) NOT NULL,
cent GEOMETRY('Point', 4326) NOT NULL GENERATED ALWAYS AS ( st_centroid(geom) ) STORED,
poly_area FLOAT NOT NULL GENERATED ALWAYS AS ( st_area(st_transform(geom, 31979)) ) STORED

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