discourse-legacysite-perl/site/slowtwitch.com/cgi-bin/articles/GT/SQL/Driver/PG.pm
2024-06-17 21:49:12 +10:00

662 lines
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Perl

# ==================================================================
# Gossamer Threads Module Library - http://gossamer-threads.com/
#
# GT::SQL::Driver::PG
# CVS Info : 087,071,086,086,085
# $Id: PG.pm,v 2.3 2005/10/06 00:05:51 jagerman Exp $
#
# Copyright (c) 2004 Gossamer Threads Inc. All Rights Reserved.
# ==================================================================
#
# Description: PostgreSQL driver for GT::SQL
#
package GT::SQL::Driver::PG;
# ====================================================================
use strict;
use vars qw/@ISA $ERROR_MESSAGE/;
use GT::SQL::Driver;
use GT::AutoLoader;
use DBI();
$ERROR_MESSAGE = 'GT::SQL';
@ISA = qw/GT::SQL::Driver/;
sub protocol_version { 2 }
sub connect {
my $self = shift;
my $dbh = $self->SUPER::connect(@_) or return;
# This is really a hack to get things working somewhat accurately - ideally
# all data should be in UTF8, but GT::SQL and our products do not yet have
# any provision for such, and inserting iso8859-1 data into a unicode table
# causes fatal errors about invalid utf8 sequences. So, we set it to
# latin1 here in the hopes that it won't break too much, and let the
# application deal with it. There are still inherent problems here,
# however - if the database is latin5, for example, setting this to latin1
# would make postgresql attempt to convert from latin1 -> latin5 on input
# and convert back on output, which is a potentially lossy conversion.
$dbh->do("SET NAMES 'LATIN1'");
return $dbh;
}
sub dsn {
# -----------------------------------------------------------------------------
# Creates a postgres-specific DSN, such as:
# DBI:Pg:dbname=database;host=some_hostname
# host is omitted if set to 'localhost', so that 'localhost' can be used for a
# non-network connection. If you really want to connect to localhost, use
# 127.0.0.1.
#
my ($self, $connect) = @_;
$connect->{driver} ||= 'Pg';
$connect->{host} ||= 'localhost';
$self->{driver} = $connect->{driver};
my $dsn = "DBI:$connect->{driver}:";
$dsn .= "dbname=$connect->{database}";
$dsn .= ";host=$connect->{host}" unless $connect->{host} eq 'localhost';
$dsn .= ";port=$connect->{port}" if $connect->{port};
return $dsn;
}
sub hints {
prefix_indexes => 1,
fix_index_dbprefix => 1,
case_map => 1,
ai => sub {
my ($table, $column) = @_;
my $seq = "${table}_seq";
my @q;
push @q, \"DROP SEQUENCE $seq";
push @q, "CREATE SEQUENCE $seq INCREMENT 1 START 1";
\@q;
},
drop_pk_constraint => 1
}
$COMPILE{_version} = __LINE__ . <<'END_OF_SUB';
sub _version {
my $self = shift;
return $self->{pg_version} if $self->{pg_version};
my $ver = $self->{dbh}->get_info(18); # SQL_DBMS_VERSION
if ($ver) {
local $^W;
$ver = sprintf "%.2f", $ver;
}
return $self->{pg_version} = $ver;
}
END_OF_SUB
sub _prepare_select {
# -----------------------------------------------------------------------------
# Rewrite MySQL-style LIMIT y,x into PG's nicer LIMIT x OFFSET y format
#
my ($self, $query) = @_;
$query =~ s/\bLIMIT\s+(\d+)\s*,\s*(\d+)/LIMIT $2 OFFSET $1/i;
$query;
}
sub _prepare_describe {
# ------------------------------------------------------------------
# Postgres-specific describe code
#
my ($self, $query) = @_;
$query =~ /DESCRIBE\s*(\w+)/i
or return $self->warn(CANTPREPARE => $query, "Invalid describe query: $query");
# atttypmod contains the scale and precision, but has to be extracted using bit operations:
my $prec_bits = 2**26-2**15-1; # bits 16 through 26 give the precision (given a max prec of 1000)
my $scale_bits = 2**10-1; # bits 1 through 10 give the scale + 4 (given a max scale of 1000)
<<QUERY
SELECT
a.attname as "Field",
CASE
WHEN t.typname = 'int4' THEN 'int(10)'
WHEN t.typname = 'int2' THEN 'smallint(5)'
WHEN t.typname = 'int8' THEN 'bigint(19)'
WHEN t.typname = 'float4' THEN 'real'
WHEN t.typname = 'float8' THEN 'double'
WHEN t.typname = 'bpchar' THEN 'char(' || (a.atttypmod - 4) || ')'
WHEN t.typname = 'varchar' THEN 'varchar(' || (a.atttypmod - 4) || ')'
WHEN t.typname = 'numeric' THEN 'decimal(' || ((atttypmod & $prec_bits)>>16) || ',' || ((a.atttypmod & $scale_bits)-4) || ')'
ELSE t.typname
END AS "Type",
CASE WHEN a.attnotnull = 't' THEN '' ELSE 'YES' END AS "Null",
(
SELECT
CASE
WHEN adsrc SIMILAR TO '''%''::[a-zA-Z0-9]+' THEN substring(adsrc from '''#"%#"''::[a-zA-Z0-9]+' for '#')
WHEN adsrc SIMILAR TO '[0-9.e+-]+' THEN adsrc
ELSE NULL
END
FROM pg_attrdef
WHERE adrelid = c.relfilenode AND adnum = a.attnum
) AS "Default",
(
SELECT
CASE WHEN d.adsrc LIKE 'nextval(%)' THEN 'auto_increment' ELSE '' END
FROM pg_attrdef d
WHERE d.adrelid = c.relfilenode AND adnum = a.attnum
) AS "Extra"
FROM
pg_class c, pg_attribute a, pg_type t
WHERE
a.atttypid = t.oid AND a.attrelid = c.oid AND
relkind = 'r' AND
a.attnum > 0 AND
c.relname = '\L$1\E'
ORDER BY
a.attnum
QUERY
# The following could be used above for Key - but it's left off because SHOW
# INDEX is much more useful:
# (
# SELECT CASE WHEN COUNT(*) >= 1 THEN 'PRI' ELSE '' END
# FROM pg_index keyi, pg_class keyc, pg_attribute keya
# WHERE keyi.indexrelid = keyc.oid AND keya.attrelid = keyc.oid and keyi.indrelid = c.oid
# and indisprimary = 't' and keya.attname = a.attname
# ) AS "Key",
}
sub column_exists {
my ($self, $table, $column) = @_;
my $sth = $self->{dbh}->prepare(<<EXISTS);
SELECT
COUNT(*)
FROM
pg_class c, pg_attribute a
WHERE
a.attrelid = c.oid AND
c.relkind = 'r' AND a.attnum > 0 AND
c.relname = ? AND a.attname = ?
EXISTS
$sth->execute(lc $table, lc $column);
return scalar $sth->fetchrow;
}
sub _prepare_show_tables {
# -----------------------------------------------------------------------------
# pg-specific 'SHOW TABLES'-equivelant
#
<<' QUERY';
SELECT relname AS tables
FROM pg_class
WHERE relkind = 'r' AND NOT (relname LIKE 'pg_%' OR relname LIKE 'sql_%')
ORDER BY relname
QUERY
}
sub _prepare_show_index {
# -----------------------------------------------------------------------------
# Get index list
#
my ($self, $query) = @_;
unless ($query =~ /^\s*SHOW\s+INDEX\s+FROM\s+(\w+)\s*$/i) {
return $self->warn(CANTPREPARE => $query, "Invalid/unsupported SHOW INDEX query: $query");
}
<<" QUERY";
SELECT
c.relname AS index_name,
attname AS index_column,
CASE WHEN indisunique = 't' THEN 1 ELSE 0 END AS index_unique,
CASE WHEN indisprimary = 't' THEN 1 ELSE 0 END AS index_primary
FROM
pg_index i,
pg_class c,
pg_class t,
pg_attribute a
WHERE
i.indexrelid = c.oid AND
a.attrelid = c.oid AND
i.indrelid = t.oid AND
t.relname = '\L$1\E'
ORDER BY
i.indexrelid, a.attnum
QUERY
}
sub drop_table {
# -----------------------------------------------------------------------------
# Drops the table passed in - drops a sequence if needed. Takes a second
# argument that, if true, causes the sequence _not_ to be dropped - used when
# the table is being recreated.
#
my ($self, $table) = @_;
my $sth = $self->{dbh}->prepare("SELECT relname FROM pg_class WHERE relkind = 'S' AND relname = '\L$table\E_seq'");
$sth->execute();
if (my $seq_name = $sth->fetchrow) {
$self->do("DROP SEQUENCE $seq_name")
or $self->warn(CANTEXECUTE => "DROP SEQUENCE $seq_name", $GT::SQL::error);
}
return $self->SUPER::drop_table($table);
}
sub drop_column {
# -------------------------------------------------------------------
# Drops a column from a table.
#
my ($self, $table, $column) = @_;
my $ver = $self->_version();
# Postgresql 7.3 and above support ALTER TABLE $table DROP $column
return $self->SUPER::drop_column($table, $column) if $ver and $ver >= 7.03;
$self->_recreate_table();
}
$COMPILE{_recreate_table} = __LINE__ . <<'END_OF_SUB';
sub _recreate_table {
# -----------------------------------------------------------------------------
# Adds/removes/changes a column, but very expensively as it involves recreating
# and copying the entire table. Takes argument pairs, currently:
#
# with => 'adding_this_column' # optional
#
# Keep in mind that the various columns depend on the {cols} hash of the table
# having been updated to reflect the change.
#
# We absolutely require DBI 1.20 in this subroutine for transaction support.
# However, we won't get here if using PG >= 7.3, so you can have either an
# outdated PG, or an outdated DBI, but not both.
#
my ($self, %opts) = @_;
DBI->require_version(1.20);
my $ver = $self->_version;
my $table = $self->{name} or $self->fatal(BADARGS => 'No table specified');
my $cols = $self->{schema}->{cols};
my %pos = map { $_ => $cols->{$_}->{pos} } keys %$cols;
my (@copy_cols, @select_cols);
for (keys %$cols) {
push @copy_cols, "$_ " . $self->column_sql($cols->{$_});
push @select_cols, $_;
}
if ($opts{with}) { # a column was added, so we can't select it from the old table
@select_cols = grep $_ ne $opts{with}, @select_cols;
}
$self->{dbh}->begin_work;
my $temptable = "GTTemp" . substr(time, -4) . int rand 10000;
my $select_cols = join ', ', @select_cols;
my $lock = "LOCK TABLE $table";
my $createtemp = "CREATE TABLE $temptable AS SELECT * FROM $table";
my $insert = "INSERT INTO $table ( $select_cols ) SELECT $select_cols FROM $temptable";
my $drop_temp = "DROP TABLE $temptable";
for my $precreate ($lock, $createtemp) {
unless ($self->{dbh}->do($precreate)) {
$self->warn(CANTEXECUTE => $precreate => $DBI::errstr);
$self->{dbh}->rollback;
return undef;
}
}
unless ($self->drop_table($table)) {
$self->{dbh}->rollback;
return undef;
}
unless ($self->create_table) {
$self->{dbh}->rollback;
return undef;
}
for my $postcreate ($insert, $drop_temp) {
unless ($self->{dbh}->do($postcreate)) {
$self->warn(CANTEXECUTE => $postcreate => $DBI::errstr);
$self->{dbh}->rollback;
return undef;
}
}
$self->{dbh}->commit;
return 1;
}
END_OF_SUB
sub alter_column {
# -----------------------------------------------------------------------------
# Changes a column in a table. The actual path done depends on multiple
# things, including your version of postgres. The following are supported
# _without_ recreating the table; anything more complicated requires the table
# be recreated via _recreate_table().
#
# - changing/dropping a default, with >= 7.0 (doesn't require DBI >= 1.20,
# everything else does)
# - adding/dropping a not null contraint, with >= 7.3
# - any other changes, with >= 7.3, by adding a new column, copying data into
# it, dropping the old column
#
# Anything else calls _recreate_table(), which also requires DBI 1.20, but is
# much more involved as the table has to be dropped and recreated.
#
my ($self, $table, $column, $new_def, $old_col) = @_;
my $ver = $self->_version;
return $self->_recreate_table() if $ver < 7;
my $cols = $self->{schema}->{cols};
my $new_col = $cols->{$column};
my @onoff = qw/not_null/; # true/false attributes
my @changeable = qw/default size scale precision/; # changeable attributes
my %add = map { ($new_col->{$_} and not $old_col->{$_}) ? ($_ => 1) : () } @onoff;
my %rem = map { ($old_col->{$_} and not $new_col->{$_}) ? ($_ => 1) : () } @onoff;
my %change = map { (
exists $new_col->{$_} and exists $old_col->{$_} # exists in both old and new
and (
defined($new_col->{$_}) ne defined($old_col->{$_}) # one is undef, the other isn't
or
defined $new_col->{$_} and defined $old_col->{$_} and $new_col->{$_} ne $old_col->{$_} # both are defined, but !=
)
) ? ($_ => 1) : () } @changeable;
{
my %add_changeable = map { (exists $new_col->{$_} and not exists $old_col->{$_}) ? ($_ => 1) : () } @changeable;
my %rem_changeable = map { (exists $old_col->{$_} and not exists $new_col->{$_}) ? ($_ => 1) : () } @changeable;
%add = (%add, %add_changeable);
%rem = (%rem, %rem_changeable);
}
if ($ver < 7.03) {
# In 7.0 - 7.2, defaults can be added/dropped/changed, but anything
# more complicated needs a table recreation
if (
keys %change == 1 and exists $change{default} and not keys %add and not keys %rem # Changed a default
or keys %add == 1 and exists $add{default} and not keys %change and not keys %rem # Added a default
or keys %rem == 1 and exists $rem{default} and not keys %change and not keys %add # Dropped a default
) {
my $query = "ALTER TABLE $table ALTER COLUMN $column ";
my $ph;
if ($add{default} or $change{default}) {
$query .= "SET DEFAULT ?";
$ph = $new_col->{default};
}
else {
$query .= "DROP DEFAULT";
}
$self->{dbh}->do($query, defined $ph ? (undef, $ph) : ())
or return $self->warn(CANTEXECUTE => $query => $DBI::errstr);
return 1;
}
return $self->_recreate_table();
}
# PG 7.3 or later
if (
keys %rem == 1 and $rem{not_null} and not keys %add and not keys %change # DROP NOT NULL
or keys %add == 1 and $add{not_null} and not keys %rem and not keys %change # SET NOT NULL
) {
# All we're doing is changing a not_null constraint
my $query = "ALTER TABLE $table ALTER COLUMN $column ";
$query .= $rem{not_null} ? 'DROP' : 'SET';
$query .= ' NOT NULL';
$self->{dbh}->do($query)
or return $self->warn(CANTEXECUTE => $query => $DBI::errstr);
return 1;
}
if (keys(%change) - ($change{default} ? 1 : 0) - (($ver >= 8 and $change{type}) ? 1 : 0) == 0 # No changes other than 'default' (and type, for PG >= 8)
and keys(%add) - ($add{default} ? 1 : 0) - ($add{not_null} ? 1 : 0) == 0 # No adds other than default or not_null
and keys(%rem) - ($rem{default} ? 1 : 0) - ($rem{not_null} ? 1 : 0) == 0 # No rems other than default or not_null
) {
my @query;
# Change type (PG 8+ only)
if ($ver >= 8 and $change{type}) {
push @query, "ALTER TABLE $table ALTER COLUMN $column TYPE $new_col->{type}";
}
# Change default
if ($add{default} or $change{default}) {
push @query, ["ALTER TABLE $table ALTER COLUMN $column SET DEFAULT ?", $new_col->{default}];
}
elsif ($rem{default}) {
push @query, "ALTER TABLE $table ALTER COLUMN $column DROP DEFAULT";
}
# Change not_null
if ($rem{not_null}) {
push @query, "ALTER TABLE $table ALTER COLUMN $column DROP NOT NULL";
}
elsif ($add{not_null}) {
if ($add{default}) {
push @query, ["UPDATE $table SET $column = ? WHERE $column IS NULL", $new_col->{default}];
}
push @query, "ALTER TABLE $table ALTER COLUMN $column SET NOT NULL";
}
return $self->do_raw_transaction(@query);
}
# We've got more complex changes than PG's ALTER COLUMN can handle; we need
# to add a new column, copy the data, drop the old column, and rename the
# new one to the old name.
my (@queries, %index, %unique);
push @queries, "LOCK TABLE $table";
my %add_def = %$new_col;
my $not_null = delete $add_def{not_null};
my $default = delete $add_def{default};
my $add_def = $self->column_sql(\%add_def);
my $tmpcol = 'GTTemp' . substr(time, -4) . int(rand 10000);
push @queries, "ALTER TABLE $table ADD COLUMN $tmpcol $add_def";
push @queries, "UPDATE $table SET $tmpcol = $column";
push @queries, ["UPDATE $table SET $tmpcol = ? WHERE $tmpcol IS NULL", $default] if $add{not_null} and defined $default;
push @queries, ["ALTER TABLE $table ALTER COLUMN $tmpcol SET DEFAULT ?", $default] if defined $default;
push @queries, "ALTER TABLE $table ALTER COLUMN $tmpcol SET NOT NULL" if $not_null;
push @queries, "ALTER TABLE $table DROP COLUMN $column";
push @queries, "ALTER TABLE $table RENAME COLUMN $tmpcol TO $column";
for my $type (qw/index unique/) {
while (my ($index, $columns) = each %{$new_col->{$type}}) {
my $recreate;
for (@$columns) {
if ($_ eq $column) {
$recreate = 1;
last;
}
}
next unless $recreate;
if ($type eq 'index') {
$index{$index} = $columns;
}
else {
$unique{$index} = $columns;
}
}
}
$self->do_raw_transaction(@queries);
while (my ($index, $columns) = each %index) {
$self->create_index($table, $index, @$columns);
}
while (my ($index, $columns) = each %unique) {
$self->create_unique($table, $index, @$columns);
}
1;
}
sub add_column {
# -----------------------------------------------------------------------------
# Adds a new column to the table.
#
my ($self, $table, $column, $def) = @_;
# make a copy so the original reference doesn't get clobbered
my %col = %{$self->{schema}->{cols}->{$column}};
# Defaults and not_null have to be set _after_ adding the column.
my $default = delete $col{default};
my $not_null = delete $col{not_null};
my $ver = $self->_version;
return $self->_recreate_table(with => $column)
if $ver < 7 and defined $default or $ver < 7.03 and $not_null;
my @queries;
if (defined $default or $not_null) {
$def = $self->column_sql(\%col);
}
push @queries, ["ALTER TABLE $table ADD $column $def"];
push @queries, ["ALTER TABLE $table ALTER COLUMN $column SET DEFAULT ?", $default] if defined $default;
push @queries, ["UPDATE $table SET $column = ?", $default] if defined $default and $not_null;
push @queries, ["ALTER TABLE $table ALTER COLUMN $column SET NOT NULL"] if $not_null;
$self->do_raw_transaction(@queries);
}
sub create_pk {
my ($self, $table, @cols) = @_;
my $ver = $self->_version;
if ($ver < 7.2) {
return $self->do("ALTER TABLE $table ADD PRIMARY KEY (" . join(',', @cols) . ")");
}
else {
# ALTER TABLE ... ADD PRIMARY KEY (...) was added in PG 7.2 - on prior
# versions we have to recreate the entire table.
return $self->_recreate_table();
}
}
sub drop_pk {
# -----------------------------------------------------------------------------
# Drop a primary key. Look for the primary key, then call drop_index with it.
#
my ($self, $table) = @_;
my $sth = $self->prepare("SHOW INDEX FROM $table") or return;
$sth->execute or return;
my $pk_name;
while (my $index = $sth->fetchrow_hashref) {
if ($index->{index_primary}) {
$pk_name = $index->{index_name};
last;
}
}
$pk_name or return $self->warn(CANTEXECUTE => "ALTER TABLE $table DROP PRIMARY KEY" => "No primary key found for $table");
$self->do("ALTER TABLE $table DROP CONSTRAINT $pk_name");
}
sub ai_insert {
my ($self, $ai) = @_;
return $ai, "NEXTVAL('$self->{name}_seq')";
}
sub insert_multiple {
# -----------------------------------------------------------------------------
# Performs multiple insertions in a single transaction, for much better speed.
#
my $self = shift;
# ->begin_work and ->commit were not added until 1.20
return $self->SUPER::insert_multiple(@_) if $DBI::VERSION < 1.20;
$self->{dbh}->begin_work;
my ($cols, $args) = @_;
my $names = join ",", @$cols, $self->{schema}->{ai} || ();
my $ret;
my $ai_insert = $self->{schema}->{ai} ? "NEXTVAL('$self->{name}_seq')" : undef;
my $query = "INSERT INTO $self->{name} ($names) VALUES (" . join(',', ('?') x @$cols, $ai_insert || ()) . ')';
my $sth = $self->{dbh}->prepare($query) or return $self->warn(CANTPREPARE => $query);
for (@$args) {
if ($sth->execute(@$_)) {
++$ret;
}
else {
$self->warn(CANTEXECUTE => $query);
}
}
$self->{dbh}->commit;
$ret;
}
sub quote {
# -----------------------------------------------------------------------------
# This subroutines quotes (or not) a value. Postgres can't handle any text
# fields containing null characters, so this has to go beyond the ordinary
# quote() in GT::SQL::Driver by stripping out null characters.
#
my $val = pop;
return 'NULL' if not defined $val;
return $$val if ref $val eq 'SCALAR' or ref $val eq 'LVALUE';
$val =~ y/\x00//d;
(values %GT::SQL::Driver::CONN)[0]->quote($val);
}
package GT::SQL::Driver::PG::sth;
# ====================================================================
use strict;
use vars qw/@ISA $ERROR_MESSAGE/;
use GT::SQL::Driver;
use GT::AutoLoader;
$ERROR_MESSAGE = 'GT::SQL';
@ISA = qw/GT::SQL::Driver::sth/;
sub insert_id {
# -------------------------------------------------------------------
# Retrieves the current sequence.
#
my $self = shift;
my ($table) = $self->{query} =~ /\s*insert\s*into\s*(\w+)/i;
$table ||= $self->{name};
my $query = "SELECT CURRVAL('${table}_seq')";
my $sth = $self->{dbh}->prepare($query) or return $self->fatal(CANTPREPARE => $query => $DBI::errstr);
$sth->execute or return $self->fatal(CANTEXECUTE => $query => $DBI::errstr);
my $id = $sth->fetchrow;
return $id;
}
# ------------------------------------------------------------------------------------------------ #
# DATA TYPE MAPPINGS
# ------------------------------------------------------------------------------------------------ #
package GT::SQL::Driver::PG::Types;
# ===============================================================
use strict;
use GT::SQL::Driver::Types;
use Carp qw/croak/;
use vars qw/@ISA/;
@ISA = 'GT::SQL::Driver::Types';
sub DATETIME { $_[0]->base($_[1], 'TIMESTAMP WITHOUT TIME ZONE') }
sub TIMESTAMP { $_[0]->base($_[1], 'TIMESTAMP WITHOUT TIME ZONE') }
sub TIME { $_[0]->base($_[1], 'TIME WITHOUT TIME ZONE') }
sub YEAR { croak "PostgreSQL does not support 'YEAR' columns" }
# Postgres doesn't have BLOB's, but has a binary 'BYTEA' type - the one (big)
# caveat to this type, however, is that it requires escaping for any input, and
# unescaping for any output.
1;