---
name: "SnowPg"
section: "3pm"
platform: "linux"
package: "libsnowpg-perl"
version: "1.15-1"
release: "Debian 5.0 (Lenny)"
platforms: ["linux"]
url: "https://new.carta.tech/SnowPg"
---

# SnowPg(3pm)

SnowPg - A simple wrapper class for Pg. use SnowPg;\
 **Connecting to the database** # Connect to the database and don't kill the connection even when `$db` goes # out of scope. If a connection is already found open matching supplied # connection string, it will be used (with a rollback if necessary)

```
        $db = SnowPg->new(connect_string => 'dbname=abc user=123',
                persist => 0,           # don't re-use connections
                debug => 1,             # send debug info to STDERR
                debugfile => '/var/log/db.log',         # append debug info to db.log
        );
```

**Performing queries**

```
        $db->query( q[SELECT %q AS Quoted], 'quoted escaped string' );
```

```
        # %q    => quoted and escaped
        #       eg. bl'ah -> 'bl\'ah'
        #           undef -> NULL
```

```
        # %l    => quoted list of strings
        #       eg. [ 'one', 'two' ]  -> 'one','two'
        #           [ @list ] ->  'abc','def'
        #               etc..
```

```
        # %u    => unquoted and unescaped (e.g. for numerical)
        #       eg. 12345 -> 12345
        #           undef -> NULL
```

```
        # %n    => boolean evaluated to NULL or NOT NULL
        #       eg. 0 or empty set or undef -> NULL
        #           1 -> NOT NULL
```

```
        # %b    => boolean evaluated to 't' or 'f'
        #       eg. 1 -> 't'
        #           0 -> 'f'
        #           undef -> NULL
```

```
        # %x    => bytea escaping (see below)
```

**Fetching query results** # Number of result rows

```
        $n = $db->ntuples();
```

\# Get a single row of results

```
        if (%result = $db->fetchrow) {
                $quoted = $result{quoted};
        }
```

\# Get multiple rows of results

```
        # Spelling it out
                while (%res = $db->fetchrow()) {
                        foreach $k (keys %res) {
                                print "$k = $res{$k}\n";
                        }
                }
```

```
        # Getting a single column of rows into a list
```

```
                @values = $db->fetchlist('fieldname');
```

```
        # Getting all rows into a list of hashes
```

```
                @rows = $db->fetchlist();
                # access example:
                print "Result is " . $rows[5]->{columnname};
```

```
        # Getting two columns into a hash
```

```
                %values = $db->fetchhash('fieldname1' => 'fieldname2');
```

```
        # Getting multiple columns into a hash using any field as a key
```

```
                %values = $db->fetchhash('fieldname1');
                # access example:
                foreach $key (keys %values) {
                        $field2 = $values{$key}->{fieldname2};
                        $field3 = $values{$key}->{fieldname3};
                        print "Row: $key has field2=$field2 and field3=$field3\n";
                }
                # NOTE: specifying a non-unique field will cause older rows
                # to be replaced with new rows in the order they are
                # received from the server!
```

**Transactions**

```
        $db->begin();
```

```
        $db->commit();
```

```
        $db->rollback();
        # Rollback gets called automatically if object is destroyed.
        # (Connection may be persistent)
```

**Byte array handling (BYTEA)**

```
        Simply send SnowPG the byte array as if it was a normal variable using
        query() and %q, eg:
```

```
        $db->query( q[INSERT INTO blobtable (blobcol) VALUES (%x)], $bytes );
```

```
        To decode postgres reponse, use:
```

```
        $bytes = SnowPg->unbytea( $postgres_output );
```

**PostgreSQL signalling**

```
        # (see Pg for more information)
        # To get the socket fd:
```

```
                $sock = $db->socket();
```

```
        # To get notifications:
```

```
                @notes = $db->notifies();
```

```
        # To consume input
```

```
                $db->consume();
```

Author: Andrew Snow, andrew@modulus.org