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Fix that adresses ticket #477 'Loading a PostGIS view is very slow'
git-svn-id: http://svn.osgeo.org/qgis/trunk@7071 c8812cc2-4d05-0410-92ff-de0c093fc19c
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mhugent committed Jul 15, 2007
1 parent 31e49a2 commit 5324e893bf706287b8174dbf5f952da1bd6ac1e0
Showing with 129 additions and 0 deletions.
  1. +115 −0 src/providers/postgres/qgspostgresprovider.cpp
  2. +14 −0 src/providers/postgres/qgspostgresprovider.h
@@ -1133,12 +1133,126 @@ bool QgsPostgresProvider::uniqueData(QString schemaName,
return isUnique;
}

int QgsPostgresProvider::SRCFromViewColumn(const QString& ns, const QString& relname, const QString& attname_table, const QString& attname_view, const QString& viewDefinition, SRC& result) const
{
QString newViewDefSql = "SELECT definition FROM pg_views WHERE schemaname = '" + ns + "' AND viewname = '" + relname + "'";
PGresult* newViewDefResult = PQexec(connection, (const char*)(newViewDefSql.utf8()));
int numEntries = PQntuples(newViewDefResult);

if(numEntries > 0) //relation is a view
{
QString newViewDefinition(PQgetvalue(newViewDefResult, 0, 0));

QString newAttNameView = attname_table;
QString newAttNameTable = attname_table;

//find out the attribute name of the underlying table/view
if (newViewDefinition.contains("AS"))
{
QRegExp s("(\\w+) " + QString("AS ") + QRegExp::escape(attname_table));
if (s.indexIn(newViewDefinition) != -1)
{
newAttNameTable = s.cap(1);
}
}

QString viewColumnSql = "SELECT table_schema, table_name, column_name FROM information_schema.view_column_usage WHERE view_schema = '" + ns + "' AND view_name = '" + relname + "' AND column_name = '" + newAttNameTable +"'";
PGresult* viewColumnResult = PQexec(connection, (const char*)(viewColumnSql.utf8()));
if(PQntuples(viewColumnResult) > 0)
{
QString newTableSchema = PQgetvalue(viewColumnResult, 0, 0);
QString newTableName = PQgetvalue(viewColumnResult, 0, 1);
int retvalue = SRCFromViewColumn(newTableSchema, newTableName, newAttNameTable, newAttNameView, newViewDefinition, result);
PQclear(viewColumnResult);
return retvalue;
}
else
{
PQclear(viewColumnResult);
return 1;
}

}

PQclear(newViewDefResult);

//relation is table, we just have to add the type
QString typeSql = "SELECT pg_type.typname FROM pg_attribute, pg_class, pg_namespace, pg_type WHERE pg_class.relname = '" + relname + "' AND pg_namespace.nspname = '" + ns + "' AND pg_attribute.attname = '" + attname_table + "' AND pg_attribute.attrelid = pg_class.oid AND pg_class.relnamespace = pg_namespace.oid AND pg_attribute.atttypid = pg_type.oid";
PGresult* typeSqlResult = PQexec(connection, (const char*)(typeSql.utf8()));
if(PQntuples(typeSqlResult) < 1)
{
return 1;
}
QString type = PQgetvalue(typeSqlResult, 0, 0);
PQclear(typeSqlResult);

result.schema=ns;
result.relation=relname;
result.column=attname_table;
result.type=type;
return 0;
}

// This function will return in the cols variable the
// underlying view and columns for each column in
// mSchemaName.mTableName.

void QgsPostgresProvider::findColumns(tableCols& cols)
{
QString viewColumnSql = "SELECT table_schema, table_name, column_name FROM information_schema.view_column_usage WHERE view_schema = '" + mSchemaName + "' AND view_name = '" + mTableName + "'";
PGresult* viewColumnResult = PQexec(connection, (const char*)(viewColumnSql.utf8()));

//find out view definition
QString viewDefSql = "SELECT definition FROM pg_views WHERE schemaname = '" + mSchemaName + "' AND viewname = '" + mTableName + "'";
PGresult* viewDefResult = PQexec(connection, (const char*)(viewDefSql.utf8()));
if(PQntuples(viewDefResult) < 1)
{
PQclear(viewDefResult);
return;
}
QString viewDefinition(PQgetvalue(viewDefResult, 0, 0));
PQclear(viewDefResult);

QString ns, relname, attname_table, attname_view;
SRC columnInformation;

for(int i = 0; i < PQntuples(viewColumnResult); ++i)
{
ns = PQgetvalue(viewColumnResult, i, 0);
relname = PQgetvalue(viewColumnResult, i, 1);
attname_table = PQgetvalue(viewColumnResult, i, 2);

//find out original attribute name
attname_view = attname_table;

//examine if the column name has been renamed in the view with AS
if (viewDefinition.contains("AS"))
{
// This regular expression needs more testing. Since the view
// definition comes from postgresql and has been 'standardised', we
// don't need to deal with everything that the user could put in a view
// definition. Does the regexp have to deal with the schema??

QRegExp s(".* \"?" + QRegExp::escape(relname) +
"\"?\\.\"?" + QRegExp::escape(attname_table) +
"\"? AS \"?(\\w+)\"?,* .*");

QgsDebugMsg(viewDefinition + "\n" + s.pattern());

if (s.indexIn(viewDefinition) != -1)
{
attname_view = s.cap(1);
qWarning("original view column name was: " + attname_view);
}
}

SRCFromViewColumn(ns, relname, attname_table, attname_view, viewDefinition, columnInformation);
cols.insert(std::make_pair(attname_view, columnInformation));
QgsDebugMsg("Inserting into cols (for key " + attname_view + " ): " + columnInformation.schema + "." + columnInformation.relation + "." + columnInformation.column + "." + columnInformation.type);
}
PQclear(viewColumnResult);

#if 0
// This sql is derived from the one that defines the view
// 'information_schema.view_column_usage' in PostgreSQL, with a few
// mods to suit our purposes.
@@ -1339,6 +1453,7 @@ void QgsPostgresProvider::findColumns(tableCols& cols)
}
}
PQclear(result);
#endif //0
}

// Returns the minimum value of an attribute
@@ -483,6 +483,20 @@ class QgsPostgresProvider:public QgsVectorDataProvider
// Function that populates the given cols structure.
void findColumns(tableCols& cols);

/**Helper function that collects information about the origin and type of a view column.
Inputs are information about the column in the underlying table
(from information_schema.view_column_usage), the attribute name
in the view and the view definition. For view columns that refer
to other views, this function calls itself until a table entry is found.
@param ns namespace of underlying table
@param relname name of underlying relation
@param attname attribute name in underlying table
@param viewDefinition definition of this view
@param result
@return 0 in case of success*/
int SRCFromViewColumn(const QString& ns, const QString& relname, const QString& attname_table,
const QString& attname_view, const QString& viewDefinition, SRC& result) const;

bool ready;
std::ofstream pLog;

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