sql: pg_sequences implemented on pg_catalog

pkg/sql/logictest/testdata/logic_test/create_statements

@@ -3110,29 +3110,29 @@ CREATE TABLE pg_catalog.pg_sequence (
    seqcycle BOOL NULL
 )  {}  {}
 CREATE TABLE pg_catalog.pg_sequences (
-   cache_size INT8 NULL,
-   cycle BOOL NULL,
-   data_type REGTYPE NULL,
-   max_value INT8 NULL,
+   schemaname NAME NULL,
+   sequencename NAME NULL,
    sequenceowner NAME NULL,
+   data_type REGTYPE NULL,
    start_value INT8 NULL,
-   increment_by INT8 NULL,
-   last_value INT8 NULL,
    min_value INT8 NULL,
-   schemaname NAME NULL,
-   sequencename NAME NULL
-)  CREATE TABLE pg_catalog.pg_sequences (
-   cache_size INT8 NULL,
-   cycle BOOL NULL,
-   data_type REGTYPE NULL,
    max_value INT8 NULL,
+   increment_by INT8 NULL,
+   cycle BOOL NULL,
+   cache_size INT8 NULL,
+   last_value INT8 NULL
+)  CREATE TABLE pg_catalog.pg_sequences (
+   schemaname NAME NULL,
+   sequencename NAME NULL,
    sequenceowner NAME NULL,
+   data_type REGTYPE NULL,
    start_value INT8 NULL,
-   increment_by INT8 NULL,
-   last_value INT8 NULL,
    min_value INT8 NULL,
-   schemaname NAME NULL,
-   sequencename NAME NULL
+   max_value INT8 NULL,
+   increment_by INT8 NULL,
+   cycle BOOL NULL,
+   cache_size INT8 NULL,
+   last_value INT8 NULL
 )  {}  {}
 CREATE TABLE pg_catalog.pg_settings (
    name STRING NULL,

pkg/sql/logictest/testdata/logic_test/pg_catalog

@@ -2015,7 +2015,7 @@ objoid      classoid    objsubid  description
 4294967155  4294967205  0         security labels (empty - feature does not exist)
 4294967156  4294967205  0         security labels (empty)
 4294967154  4294967205  0         sequences (see also information_schema.sequences)
-4294967153  4294967205  0         pg_sequences was created for compatibility and is currently unimplemented
+4294967153  4294967205  0         pg_sequences is very similar as pg_sequence.
 4294967152  4294967205  0         session variables (incomplete)
 4294967151  4294967205  0         pg_shadow was created for compatibility and is currently unimplemented
 4294967148  4294967205  0         shared dependencies (empty - not implemented)
@@ -3305,3 +3305,38 @@ SET stub_catalog_tables=true
 
 statement ok
 SELECT * FROM pg_seclabel
+
+statement ok
+CREATE SEQUENCE serial START 101 INCREMENT 5
+
+# Last value must return NULL when querying pg_sequences and sequence haven't
+# been used.
+query I
+SELECT last_value FROM pg_sequences WHERE sequencename = 'serial'
+----
+NULL
+
+statement ok
+SELECT nextval('serial');
+SELECT nextval('serial');
+SELECT nextval('serial');
+
+# Now last_value should be 111
+query TTTOIIIIBII colnames
+SELECT * FROM pg_sequences WHERE sequencename = 'serial'
+----
+schemaname  sequencename  sequenceowner  data_type  start_value  min_value  max_value            increment_by  cycle  cache_size  last_value
+public      serial        root           20         101          1          9223372036854775807  5             false  1           111
+
+# Testing sequenceowner and cache_size
+statement ok
+CREATE USER anyuser;
+GRANT CREATE ON DATABASE test TO anyuser;
+ALTER SEQUENCE serial OWNER TO anyuser;
+ALTER SEQUENCE serial CACHE 10;
+
+query TI colnames
+SELECT sequenceowner, cache_size FROM pg_sequences WHERE sequencename = 'serial'
+----
+sequenceowner  cache_size
+anyuser        10

pkg/sql/pg_catalog.go

@@ -2882,12 +2882,51 @@ var pgCatalogReplicationOriginStatusTable = virtualSchemaTable{
 }
 
 var pgCatalogSequencesTable = virtualSchemaTable{
-	comment: "pg_sequences was created for compatibility and is currently unimplemented",
-	schema:  vtable.PgCatalogSequences,
-	populate: func(ctx context.Context, p *planner, _ catalog.DatabaseDescriptor, addRow func(...tree.Datum) error) error {
-		return nil
+	comment: `pg_sequences is very similar as pg_sequence.
+https://www.postgresql.org/docs/13/view-pg-sequences.html
+`,
+	schema: vtable.PgCatalogSequences,
+	populate: func(ctx context.Context, p *planner, dbContext catalog.DatabaseDescriptor, addRow func(...tree.Datum) error) error {
+		return forEachTableDesc(ctx, p, dbContext, hideVirtual, /* virtual schemas do not have indexes */
+			func(db catalog.DatabaseDescriptor, scName string, table catalog.TableDescriptor) error {
+				if !table.IsSequence() {
+					return nil
+				}
+				opts := table.GetSequenceOpts()
+				lastValue := tree.DNull
+				sequenceValue, err := p.GetSequenceValue(ctx, p.execCfg.Codec, table)
+				if err != nil {
+					return err
+				}
+
+				// Before using for the first time, sequenceValue will be:
+				// opts.Start - opts.Increment.
+				if sequenceValue != opts.Start-opts.Increment {
+					lastValue = tree.NewDInt(tree.DInt(sequenceValue))
+				}
+
+				// sequenceowner refers to the username that owns the sequence which is
+				// available in the table descriptor that can be changed by ALTER
+				// SEQUENCE sequencename OWNER TO username. Sequence opts have a
+				// table.column owner which is the value that can be modifyied by ALTER
+				// SEQUENE sequencename OWNED BY table.column, This is not the expected
+				// value on sequenceowner.
+				return addRow(
+					tree.NewDString(scName),                 // schemaname
+					tree.NewDString(table.GetName()),        // sequencename
+					getOwnerName(table),                     // sequenceowner
+					tree.NewDOid(tree.DInt(oid.T_int8)),     // data_type
+					tree.NewDInt(tree.DInt(opts.Start)),     // start_value
+					tree.NewDInt(tree.DInt(opts.MinValue)),  // min_value
+					tree.NewDInt(tree.DInt(opts.MaxValue)),  // max_value
+					tree.NewDInt(tree.DInt(opts.Increment)), // increment_by
+					tree.DBoolFalse,                         // cycle
+					tree.NewDInt(tree.DInt(opts.CacheSize)), // cache_size
+					lastValue,                               // last_value
+				)
+			},
+		)
 	},
-	unimplemented: true,
 }
 
 // typOid is the only OID generation approach that does not use oidHasher, because

pkg/sql/vtable/pg_catalog.go

@@ -1349,17 +1349,17 @@ CREATE TABLE pg_catalog.pg_policy (
 //PgCatalogSequences is an empty table in the pg_catalog that is not implemented yet
 const PgCatalogSequences = `
 CREATE TABLE pg_catalog.pg_sequences (
-	cache_size INT,
-	cycle BOOL,
-	data_type REGTYPE,
-	max_value INT,
+	schemaname NAME,
+	sequencename NAME,
 	sequenceowner NAME,
+	data_type REGTYPE,
 	start_value INT,
-	increment_by INT,
-	last_value INT,
 	min_value INT,
-	schemaname NAME,
-	sequencename NAME
+	max_value INT,
+	increment_by INT,
+	cycle BOOL,
+	cache_size INT,
+	last_value INT
 )`
 
 //PgCatalogSubscriptionRel is an empty table in the pg_catalog that is not implemented yet