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qgsvirtuallayerqueryparser.cpp
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qgsvirtuallayerqueryparser.cpp
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/***************************************************************************
qgsvirtuallayerqueryparser.cpp : SQL query parser utility functions
begin : Jan 2016
copyright : (C) 2016 Hugo Mercier, Oslandia
email : hugo dot mercier at oslandia dot com
***************************************************************************/
/***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/
#include "qgsvirtuallayerqueryparser.h"
#include "qgsvirtuallayersqlitehelper.h"
#include "qgsvirtuallayerblob.h"
#include <QRegExp>
#include <QtDebug>
namespace QgsVirtualLayerQueryParser
{
QStringList referencedTables( const QString& query )
{
QStringList tables;
//
// open an empty in-memory sqlite database and execute the query
// sqlite will return an error for each missing table
// this way we know the list of tables referenced by the query
QgsScopedSqlite db( ":memory:", /*withExtension=*/ false );
const QString noSuchError = "no such table: ";
while ( true )
{
char *errMsg = nullptr;
int r = sqlite3_exec( db.get(), query.toUtf8().constData(), nullptr, nullptr, &errMsg );
QString err = QString::fromUtf8( errMsg );
if ( r && err.startsWith( noSuchError ) )
{
QString tableName = err.mid( noSuchError.size() );
tables << tableName;
// create a dummy table to skip this error
QString createStr = QString( "CREATE TABLE \"%1\" (id int)" ).arg( tableName.replace( "\"", "\"\"" ) );
( void )sqlite3_exec( db.get(), createStr.toUtf8().constData(), nullptr, NULL, NULL );
}
else
{
// no error, or another error
break;
}
}
return tables;
}
QMap<QString, ColumnDef> columnCommentDefinitions( const QString& query )
{
QMap<QString, ColumnDef> defs;
// look for special comments in SQL
// a column name followed by /*:type*/
QRegExp rx( "([a-zA-Z_\x80-\xFF][a-zA-Z0-9_\x80-\xFF]*)\\s*/\\*:(int|real|text|((?:multi)?(?:point|linestring|polygon)):(\\d+))\\s*\\*/", Qt::CaseInsensitive );
int pos = 0;
while (( pos = rx.indexIn( query, pos ) ) != -1 )
{
QString column = rx.cap( 1 );
QString type = rx.cap( 2 );
ColumnDef def;
def.setName( column );
if ( type == "int" )
def.setScalarType( QVariant::Int );
else if ( type == "real" )
def.setScalarType( QVariant::Double );
else if ( type == "text" )
def.setScalarType( QVariant::String );
else
{
// there should be 2 more captures
def.setGeometry( QgsWKBTypes::parseType( rx.cap( 3 ) ) );
def.setSrid( static_cast<QgsWKBTypes::Type>( rx.cap( 4 ).toLong() ) );
}
defs[column] = def;
pos += rx.matchedLength();
}
return defs;
}
// set the type of the column type, given its text representation
void setColumnDefType( const QString& columnType, ColumnDef& d )
{
// geometry type
QRegExp geometryTypeRx( "\\(([0-9]+),([0-9]+)\\)" );
// see qgsvirtuallayersqlitemodule for possible declared types
// the type returned by PRAGMA table_info will be either
// the type declared by one of the virtual tables
// or null
if ( columnType == "int" )
d.setScalarType( QVariant::Int );
else if ( columnType == "real" )
d.setScalarType( QVariant::Double );
else if ( columnType == "text" )
d.setScalarType( QVariant::String );
else if ( columnType.startsWith( "geometry" ) )
{
// parse the geometry type and srid
// geometry(type,srid)
int pos = geometryTypeRx.indexIn( columnType, 0 );
if ( pos != -1 )
{
QgsWKBTypes::Type type = static_cast<QgsWKBTypes::Type>( geometryTypeRx.cap( 1 ).toInt() );
long srid = geometryTypeRx.cap( 2 ).toLong();
d.setGeometry( type );
d.setSrid( srid );
}
}
}
ColumnDef geometryDefinitionFromVirtualTable( sqlite3* db, const QString& tableName )
{
ColumnDef d;
Sqlite::Query q( db, QString( "PRAGMA table_info(%1)" ).arg( tableName ) );
while ( q.step() == SQLITE_ROW )
{
QString columnName = q.columnText( 1 );
QString columnType = q.columnText( 2 );
if ( ! columnType.startsWith( "geometry" ) )
continue;
d.setName( columnName );
setColumnDefType( columnType, d );
break;
}
return d;
}
TableDef columnDefinitionsFromQuery( sqlite3* db, const QString& query )
{
// get column types defined by comments
QMap<QString, ColumnDef> definedColumns = columnCommentDefinitions( query );
// create a view to detect column names and types, using PRAGMA table_info
QString viewStr = "CREATE TEMP VIEW _tview AS " + query;
Sqlite::Query::exec( db, viewStr );
QStringList columns;
QVector<int> undefinedColumns;
TableDef tableDef;
{
Sqlite::Query q( db, "PRAGMA table_info(_tview)" );
int columnNumber = 0;
while ( q.step() == SQLITE_ROW )
{
QString columnName = q.columnText( 1 );
columns << columnName;
QString columnType = q.columnText( 2 );
// column type defined by comments
if ( definedColumns.contains( columnName ) )
{
tableDef << definedColumns[columnName];
}
else
{
ColumnDef d;
d.setName( columnName );
setColumnDefType( columnType, d );
if ( d.scalarType() == QVariant::Invalid )
{
// else no type is defined
undefinedColumns << columnNumber;
}
tableDef << d;
}
columnNumber++;
}
}
if ( undefinedColumns.size() == 0 )
return tableDef;
// get the first row to introspect types
{
QString qs = "SELECT ";
for ( int i = 0; i < undefinedColumns.size(); i++ )
{
qs += "\"" + columns[undefinedColumns[i]] + "\"";
if ( i != undefinedColumns.size() - 1 )
qs += ", ";
}
qs += " FROM _tview LIMIT 1";
qWarning() << qs;
Sqlite::Query q( db, qs );
if ( q.step() == SQLITE_ROW )
{
for ( int i = 0; i < undefinedColumns.size(); i++ )
{
int colIdx = undefinedColumns[i];
int type = q.columnType( i );
switch ( type )
{
case SQLITE_INTEGER:
tableDef[colIdx].setScalarType( QVariant::Int );
break;
case SQLITE_FLOAT:
tableDef[colIdx].setScalarType( QVariant::Double );
break;
case SQLITE_BLOB:
{
// might be a geometry, parse the type
QByteArray ba( q.columnBlob( i ) );
QPair<QgsWKBTypes::Type, long> p( spatialiteBlobGeometryType( ba.constData(), ba.size() ) );
if ( p.first != QgsWKBTypes::NoGeometry )
{
tableDef[colIdx].setGeometry( p.first );
tableDef[colIdx].setSrid( p.second );
}
else
{
// interpret it as a string
tableDef[colIdx].setScalarType( QVariant::String );
}
}
break;
case SQLITE_TEXT:
default:
tableDef[colIdx].setScalarType( QVariant::String );
break;
};
}
}
}
return tableDef;
}
TableDef tableDefinitionFromVirtualTable( sqlite3* db, const QString& tableName )
{
TableDef td;
Sqlite::Query q( db, QString( "PRAGMA table_info(%1)" ).arg( tableName ) );
while ( q.step() == SQLITE_ROW )
{
ColumnDef d;
QString columnName = q.columnText( 1 );
QString columnType = q.columnText( 2 );
d.setName( columnName );
setColumnDefType( columnType, d );
td << d;
}
return td;
}
} // namespace