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Postgres FD Implementation
Commit 57040f78 authored by Bruce Momjian's avatar Bruce Momjian
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Attached is a patch for JDBC's getColumn() function that was broken / 

flawed in the following ways:

1. Only returned columns that had a default value defined, rather than all
columns in a table
2. Used 2 * N + 1 queries to find out attributes, comments and typenames
for N columns.

By using some outer join syntax it is possible to retrieve all necessary
information in just one SQL statement. This means this version is only
suitable for PostgreSQL >= 7.1. Don't know whether that's a problem.

I've tested this function with current sources and 7.1.3 and patched both
jdbc1 and jdbc2. I haven't compiled nor tested the jdbc1 version though, as
I have no JDK 1.1 available.

Note the discussion in http://fts.postgresql.org/db/mw/msg.html?mid=1029626
regarding differences in obtaining comments on database object in 7.1 and
7.2. I was unable to use the following syntax (or similar ones):

select
     ...,
     description
from
     ...
     left outer join col_description(a.attrelid, a.attnum) description
order by
     c.relname, a.attnum;

(the error was parse error at or near '(') so I had to paste the actual
code for the col_description function into the left outer join. Maybe
someone who is more knowledgable about outer joins might provide me with a
better SQL statement.

Jeroen van Vianen
parent 0b71596f
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Showing with 230 additions and 193 deletions
src/interfaces/jdbc/org/postgresql/jdbc1/DatabaseMetaData.java
View file @ 57040f78
......@@ -13,6 +13,8 @@ import org.postgresql.util.PSQLException;
/**
* This class provides information about the database as a whole.
*
* $Id: DatabaseMetaData.java,v 1.30 2001/09/06 03:20:30 momjian Exp $
*
* <p>Many of the methods here return lists of information in ResultSets. You
* can use the normal ResultSet methods such as getString and getInt to
* retrieve the data from these ResultSets. If a given form of metadata is
......@@ -1893,21 +1895,19 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
*/
public java.sql.ResultSet getColumns(String catalog, String schemaPattern, String tableNamePattern, String columnNamePattern) throws SQLException
{
// the field descriptors for the new ResultSet
Field f[] = new Field[18];
java.sql.ResultSet r; // ResultSet for the SQL query that we need to do
Vector v = new Vector(); // The new ResultSet tuple stuff
f[0] = new Field(connection, "TABLE_CAT", iVarcharOid, 32);
f[1] = new Field(connection, "TABLE_SCHEM", iVarcharOid, 32);
f[2] = new Field(connection, "TABLE_NAME", iVarcharOid, 32);
f[3] = new Field(connection, "COLUMN_NAME", iVarcharOid, 32);
f[4] = new Field(connection, "DATA_TYPE", iInt2Oid, 2);
f[5] = new Field(connection, "TYPE_NAME", iVarcharOid, 32);
f[6] = new Field(connection, "COLUMN_SIZE", iInt4Oid, 4);
f[7] = new Field(connection, "BUFFER_LENGTH", iVarcharOid, 32);
f[8] = new Field(connection, "DECIMAL_DIGITS", iInt4Oid, 4);
f[9] = new Field(connection, "NUM_PREC_RADIX", iInt4Oid, 4);
Field f[] = new Field[18]; // The field descriptors for the new ResultSet
f[ 0] = new Field(connection, "TABLE_CAT", iVarcharOid, 32);
f[ 1] = new Field(connection, "TABLE_SCHEM", iVarcharOid, 32);
f[ 2] = new Field(connection, "TABLE_NAME", iVarcharOid, 32);
f[ 3] = new Field(connection, "COLUMN_NAME", iVarcharOid, 32);
f[ 4] = new Field(connection, "DATA_TYPE", iInt2Oid, 2);
f[ 5] = new Field(connection, "TYPE_NAME", iVarcharOid, 32);
f[ 6] = new Field(connection, "COLUMN_SIZE", iInt4Oid, 4);
f[ 7] = new Field(connection, "BUFFER_LENGTH", iVarcharOid, 32);
f[ 8] = new Field(connection, "DECIMAL_DIGITS", iInt4Oid, 4);
f[ 9] = new Field(connection, "NUM_PREC_RADIX", iInt4Oid, 4);
f[10] = new Field(connection, "NULLABLE", iInt4Oid, 4);
f[11] = new Field(connection, "REMARKS", iVarcharOid, 32);
f[12] = new Field(connection, "COLUMN_DEF", iVarcharOid, 32);
......@@ -1917,91 +1917,110 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
f[16] = new Field(connection, "ORDINAL_POSITION", iInt4Oid,4);
f[17] = new Field(connection, "IS_NULLABLE", iVarcharOid, 32);
// Added by Stefan Andreasen <stefan@linux.kapow.dk>
// If the pattern are null then set them to %
if (tableNamePattern == null) tableNamePattern="%";
if (columnNamePattern == null) columnNamePattern="%";
// Now form the query
String query =
"select " +
(connection.haveMinimumServerVersion("7.2") ? "a.attrelid" : "a.oid") +
",c.relname,a.attname,a.atttypid," +
"a.attnum,a.attnotnull,a.attlen,a.atttypmod,d.adsrc from pg_class c," +
"pg_attribute a,pg_attrdef d where a.attrelid=c.oid and " +
"c.relname like '"+tableNamePattern.toLowerCase()+"' and " +
"a.attname like '"+columnNamePattern.toLowerCase()+"' and " +
"a.attnum>0 and c.oid=d.adrelid and d.adnum=a.attnum " +
"order by c.relname,a.attnum";
r = connection.ExecSQL(query);
while(r.next()) {
byte[][] tuple = new byte[18][0];
// Fetch the description for the table (if any)
String getDescriptionStatement =
connection.haveMinimumServerVersion("7.2") ?
"select col_description(" + r.getInt(1) + "," + r.getInt(5) + ")" :
"select description from pg_description where objoid=" + r.getInt(1);
java.sql.ResultSet dr = connection.ExecSQL(getDescriptionStatement);
if(((org.postgresql.ResultSet)dr).getTupleCount()==1) {
dr.next();
tuple[11] = dr.getBytes(1);
} else
tuple[11] = null;
dr.close();
tuple[0] = "".getBytes(); // Catalog name
tuple[1] = "".getBytes(); // Schema name
tuple[2] = r.getBytes(2); // Table name
tuple[3] = r.getBytes(3); // Column name
dr = connection.ExecSQL("select typname from pg_type where oid = "+r.getString(4));
dr.next();
String typname=dr.getString(1);
dr.close();
tuple[4] = Integer.toString(connection.getSQLType(typname)).getBytes(); // Data type
tuple[5] = typname.getBytes(); // Type name
// Column size
// Looking at the psql source,
// I think the length of a varchar as specified when the table was created
// should be extracted from atttypmod which contains this length + sizeof(int32)
if (typname.equals("bpchar") || typname.equals("varchar")) {
int atttypmod = r.getInt(8);
tuple[6] = Integer.toString(atttypmod != -1 ? atttypmod - VARHDRSZ : 0).getBytes();
} else
tuple[6] = r.getBytes(7);
tuple[7] = null; // Buffer length
tuple[8] = "0".getBytes(); // Decimal Digits - how to get this?
tuple[9] = "10".getBytes(); // Num Prec Radix - assume decimal
// tuple[10] is below
// tuple[11] is above
tuple[12] = r.getBytes(9); // column default
tuple[13] = null; // sql data type (unused)
tuple[14] = null; // sql datetime sub (unused)
StringBuffer sql = new StringBuffer(512);
sql.append("select " +
(connection.haveMinimumServerVersion("7.2") ? "a.attrelid, " : "a.oid, ") +
" c.relname, " +
" a.attname, " +
" a.atttypid, " +
" a.attnum, " +
" a.attnotnull, " +
" a.attlen, " +
" a.atttypmod, " +
" d.adsrc, " +
" t.typname, " +
" e.description " +
"from" +
" (" +
" (pg_class c inner join pg_attribute a on" +
" (" +
" a.attrelid=c.oid");
if ((tableNamePattern != null) && ! tableNamePattern.equals("%")) {
sql.append(" and c.relname like \'" + tableNamePattern + "\'");
}
tuple[15] = tuple[6]; // char octet length
if ((columnNamePattern != null) && ! columnNamePattern.equals("%")) {
sql.append(" and a.attname like \'" + columnNamePattern + "\'");
}
tuple[16] = r.getBytes(5); // ordinal position
sql.append(
" and a.attnum > 0" +
" )" +
" ) inner join pg_type t on" +
" (" +
" t.oid = a.atttypid" +
" )" +
" )" +
" left outer join pg_attrdef d on" +
" (" +
" c.oid = d.adrelid" +
" and a.attnum = d.adnum" +
" )" +
" left outer join pg_description e on" +
" (" +
" e.objoid = a.attrelid");
if (connection.haveMinimumServerVersion("7.2")) {
sql.append(
" and e.objsubid = a.attnum" +
" and e.classoid = (select oid from pg_class where relname = \'pg_class\')");
}
String nullFlag = r.getString(6);
tuple[10] = Integer.toString(nullFlag.equals("f")?java.sql.DatabaseMetaData.columnNullable:java.sql.DatabaseMetaData.columnNoNulls).getBytes(); // Nullable
tuple[17] = (nullFlag.equals("f")?"YES":"NO").getBytes(); // is nullable
sql.append(
" ) " +
"order by" +
" c.relname, a.attnum");
System.out.println(sql);
java.sql.ResultSet r = connection.ExecSQL(sql.toString());
while (r.next()) {
byte[][] tuple = new byte[18][0];
String nullFlag = r.getString(6);
String typname = r.getString(10);
tuple[0] = "".getBytes(); // Catalog name
tuple[1] = "".getBytes(); // Schema name
tuple[2] = r.getBytes(2); // Table name
tuple[3] = r.getBytes(3); // Column name
tuple[4] = Integer.toString(connection.getSQLType(typname)).getBytes(); // Data type
tuple[5] = typname.getBytes(); // Type name
// Column size
// Looking at the psql source,
// I think the length of a varchar as specified when the table was created
// should be extracted from atttypmod which contains this length + sizeof(int32)
if (typname.equals("bpchar") || typname.equals("varchar")) {
int atttypmod = r.getInt(8);
tuple[6] = Integer.toString(atttypmod != -1 ? atttypmod - VARHDRSZ : 0).getBytes();
} else {
tuple[6] = r.getBytes(7);
}
tuple[7] = null; // Buffer length
tuple[8] = "0".getBytes(); // Decimal Digits - how to get this?
tuple[9] = "10".getBytes(); // Num Prec Radix - assume decimal
tuple[10] = Integer.toString(nullFlag.equals("f") ?
java.sql.DatabaseMetaData.columnNullable :
java.sql.DatabaseMetaData.columnNoNulls).getBytes(); // Nullable
tuple[11] = r.getBytes(11); // Description (if any)
tuple[12] = r.getBytes(9); // Column default
tuple[13] = null; // sql data type (unused)
tuple[14] = null; // sql datetime sub (unused)
tuple[15] = tuple[6]; // char octet length
tuple[16] = r.getBytes(5); // ordinal position
tuple[17] = (nullFlag.equals("f") ? "YES" : "NO").getBytes(); // Is nullable
v.addElement(tuple);
}
r.close();
v.addElement(tuple);
}
r.close();
return new ResultSet(connection, f, v, "OK", 1);
}
/**
* Get a description of the access rights for a table's columns.
*
......
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