Schema Metadata

PHP Driver exposes the Cassandra Schema Metadata for keyspaces, tables, and columns.

Background

Given

a running Cassandra cluster

And

the following schema:

CREATE KEYSPACE simplex WITH replication = {
  'class': 'SimpleStrategy',
  'replication_factor': 1
} AND DURABLE_WRITES = false;
USE simplex;
CREATE TABLE values (
  id int PRIMARY KEY,
  bigint_value bigint,
  decimal_value decimal,
  double_value double,
  float_value float,
  int_value int,
  varint_value varint,
  ascii_value ascii,
  timestamp_value timestamp,
  blob_value blob,
  uuid_value uuid,
  timeuuid_value timeuuid,
  inet_value inet,
  list_value List<bigint>,
  map_value Map<timestamp, double>,
  set_value Set<float>
) WITH
    bloom_filter_fp_chance=0.5 AND
    comment='Schema Metadata Feature' AND
    compaction={'class': 'LeveledCompactionStrategy', 'sstable_size_in_mb' : 37} AND
    compression={'sstable_compression': 'DeflateCompressor'} AND
    dclocal_read_repair_chance=0.25 AND
    gc_grace_seconds=3600 AND
    read_repair_chance=0.75;

Getting keyspace metadata

Given

the following example:

$cluster  = Dse::cluster()->build();
$session  = $cluster->connect("simplex");

$schema   = $session->schema();
$keyspace = $schema->keyspace("simplex");

echo "Name: {$keyspace->name()}" . PHP_EOL;

/*
 * For Cassandra 2.2+ the replication class name and replication options have
 * been combined into a Map<varchar, varchar> inside the metadata 'replication'
 * instead of two metadata fields 'strategy_class' and 'strategy_options'.
 */
$replication_options = $keyspace->replicationOptions();
if ($replication_options instanceof Dse\Map &&
    count($replication_options) > 1) {
    echo "Replication Class: {$replication_options["class"]}" . PHP_EOL;
    echo "  replication_factor:{$replication_options["replication_factor"]}" . PHP_EOL;
} else {
    echo "Replication Class: {$keyspace->replicationClassName()}" . PHP_EOL;
    foreach ($replication_options as $name => $value) {
        echo "  {$name}:{$value}" . PHP_EOL;
    }
}

echo "Has Durable Writes: " . ($keyspace->hasDurableWrites() ? "True" : "False" ). PHP_EOL;

When

it is executed

Then

its output should contain:

Name: simplex
Replication Class: org.apache.cassandra.locator.SimpleStrategy
  replication_factor:1
Has Durable Writes: False

Getting table metadata

Given

the following example:

$cluster = Dse::cluster()->build();
$session = $cluster->connect("simplex");

$schema  = $session->schema();
$table   = $schema->keyspace("simplex")->table("values");

echo "Name: {$table->name()}" . PHP_EOL;
echo "Bloom Filter: {$table->bloomFilterFPChance()}" . PHP_EOL;
echo "Comment: {$table->comment()}" . PHP_EOL;

/*
 * For Cassandra 2.2+ the compaction strategy class name and compaction
 * strategy options have been combined into a Map<varchar, varchar> inside
 * the metadata 'compaction' instead of two metadata fields
 * 'compaction_strategy_class' and 'compaction_strategy_options'.
 */
$compaction_options = $table->compactionStrategyOptions();
$compression_parameters = $table->compressionParameters();
echo "Compaction Class: ";
if ($compaction_options instanceof Dse\Map &&
    count($compaction_options) > 1) {
    echo $compaction_options["class"] . PHP_EOL;
    echo "  sstable_size_in_mb: {$compaction_options["sstable_size_in_mb"]}" . PHP_EOL;
    echo "  sstable_compression: {$compression_parameters["class"]}" . PHP_EOL;
} else {
    echo $table->compactionStrategyClassName() . PHP_EOL;
    foreach ($compaction_options as $key => $value) {
        echo "  {$key}: {$value}" . PHP_EOL;
    }
    foreach ($compression_parameters as $key => $value) {
        echo "  {$key}: {$value}" . PHP_EOL;
    }
}

echo "Garbage Collection Grace Seconds: {$table->gcGraceSeconds()}" . PHP_EOL;
echo "Read Repair Chance: {$table->readRepairChance()}" . PHP_EOL;

When

it is executed

Then

its output should contain:

Name: values
Bloom Filter: 0.5
Comment: Schema Metadata Feature
Compaction Class: org.apache.cassandra.db.compaction.LeveledCompactionStrategy
  sstable_size_in_mb: 37
  sstable_compression: org.apache.cassandra.io.compress.DeflateCompressor
Garbage Collection Grace Seconds: 3600
Read Repair Chance: 0.75

until cassadra v2.1

Getting table metadata for io cache and replicate on write

Given

the following schema:

ALTER TABLE simplex.values
  WITH
    populate_io_cache_on_flush='true' AND
    replicate_on_write='false';

And

the following example:

$cluster = Dse::cluster()->build();
$session = $cluster->connect("simplex");

$schema  = $session->schema();
$table   = $schema->keyspace("simplex")->table("values");

echo "Populate I/O Cache on Flush: " . ($table->populateIOCacheOnFlush() ? "True" : "False") . PHP_EOL;
echo "Replicate on Write: " . ($table->replicateOnWrite() ? "True" : "False") . PHP_EOL;

When

it is executed

Then

its output should contain:

Populate I/O Cache on Flush: True
Replicate on Write: False

only on cassadra v2.0

Getting table metadata for index interval

Given

the following schema:

ALTER TABLE simplex.values
  WITH
    index_interval = '512';

And

the following example:

$cluster = Dse::cluster()->build();
$session = $cluster->connect("simplex");
$schema  = $session->schema();
$table   = $schema->keyspace("simplex")->table("values");

echo "Index Interval: {$table->indexInterval()}" . PHP_EOL;

When

it is executed

Then

its output should contain:

Index Interval: 512

since cassadra v2.0

Getting table metadata for default TTL, memtable flush period and speculative retry

Given

the following schema:

ALTER TABLE simplex.values
  WITH
    default_time_to_live = '10000' AND
    memtable_flush_period_in_ms = '100' AND
    speculative_retry = '10ms';

And

the following example:

$cluster = Dse::cluster()->build();
$session = $cluster->connect("simplex");
$schema  = $session->schema();
$table   = $schema->keyspace("simplex")->table("values");

echo "Default TTL: {$table->defaultTTL()}" . PHP_EOL;
echo "Memtable Flush Period: {$table->memtableFlushPeriodMs()}" . PHP_EOL;
echo "Speculative Retry: " . intval($table->speculativeRetry()) . PHP_EOL;

When

it is executed

Then

its output should contain:

Default TTL: 10000
Memtable Flush Period: 100
Speculative Retry: 10

since cassadra v2.1

Getting table metadata for max and min index intervals

Given

the following schema:

ALTER TABLE simplex.values
  WITH
    max_index_interval = '16' AND
    min_index_interval = '4';

And

the following example:

$cluster = Dse::cluster()->build();
$session = $cluster->connect("simplex");
$schema  = $session->schema();
$table   = $schema->keyspace("simplex")->table("values");

echo "Maximum Index Interval: {$table->maxIndexInterval()}" . PHP_EOL;
echo "Minimum Index Interval: {$table->minIndexInterval()}" . PHP_EOL;

When

it is executed

Then

its output should contain:

Maximum Index Interval: 16
Minimum Index Interval: 4

since cassadra v2.0

Getting metadata for column and types

Given

the following example:

$cluster   = Dse::cluster()->build();
$session   = $cluster->connect("simplex");
$schema    = $session->schema();
$table     = $schema->keyspace("simplex")->table("values");
foreach ($table->columns() as $column) {
    echo "{$column->name()}: {$column->type()}" . PHP_EOL;
}

When

it is executed

Then

its output should contain disregarding order:

ascii_value: ascii
bigint_value: bigint
blob_value: blob
decimal_value: decimal
double_value: double
float_value: float
id: int
inet_value: inet
int_value: int
list_value: list<bigint>
map_value: map<timestamp, double>
set_value: set<float>
timestamp_value: timestamp
timeuuid_value: timeuuid
uuid_value: uuid
varint_value: varint

since cassadra v2.1

Getting metadata for user types

Given

the following schema:

CREATE TYPE simplex.type1 (a int, b text);
CREATE TYPE simplex.type2 (a map<timeuuid, int>, b bigint);
CREATE TYPE simplex.type3 (a map<blob, frozen<set<varint>>>, b list<uuid>);

And

the following example:

$cluster   = Dse::cluster()->build();
$session   = $cluster->connect("simplex");
$schema    = $session->schema();
$keyspace  = $schema->keyspace("simplex");

foreach ($keyspace->userTypes() as $name => $type) {
    echo "Name: {$name}" . PHP_EOL;
    echo "Type:" . PHP_EOL;
    foreach ($type->types() as $key => $data_type) {
        echo "  {$key} => {$data_type}" . PHP_EOL;
    }
}

When

it is executed

Then

its output should contain:

Name: type1
Type:
  a => int
  b => text
Name: type2
Type:
  a => map<timeuuid, int>
  b => bigint
Name: type3
Type:
  a => map<blob, set<varint>>
  b => list<uuid>

Disable schema metadata

Given

the following example:

$cluster   = Dse::cluster()
                 ->withSchemaMetadata(false)
                 ->build();
$session   = $cluster->connect("simplex");
$schema    = $session->schema();
echo count($schema->keyspaces()) . PHP_EOL;

When

it is executed

Then

its output should contain:

Schema Metadata

Background

Getting keyspace metadata

Getting table metadata

Getting table metadata for io cache and replicate on write

Getting table metadata for index interval

Getting table metadata for default TTL, memtable flush period and speculative retry

Getting table metadata for max and min index intervals

Getting metadata for column and types

Getting metadata for user types

Disable schema metadata

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