sql: Add information_schema.statistics

[yznming]

#8675 add information_schema.statistics table.

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This change is

[nvanbenschoten]

Thanks for putting this together! I have a few comments, but the general approach looks good.

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Review status: 0 of 2 files reviewed at latest revision, 9 unresolved discussions, all commit checks successful.

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pkg/sql/information_schema.go, line 410 at r1 (raw file):

}

var informationSchemaStatisticsTable = virtualSchemaTable{

Lets move this up to be in lexicographical order.

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pkg/sql/information_schema.go, line 421 at r1 (raw file):

  SEQ_IN_INDEX INT NOT NULL DEFAULT 0,
  COLUMN_NAME STRING NOT NULL DEFAULT '',
  "COLLATION" STRING NOT NULL DEFAULT '',

Why the quotes?

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pkg/sql/information_schema.go, line 430 at r1 (raw file):

          func(db *sqlbase.DatabaseDescriptor, table *sqlbase.TableDescriptor) error {
              appendRow := func(index sqlbase.IndexDescriptor, colName string, sequence int,
                  direction string, isStored bool) error {

direction has a limited set of values (ASC, DESC, N/A). It's probably worth making constants for these values (see tableTypeSystemView)

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pkg/sql/information_schema.go, line 432 at r1 (raw file):

                  direction string, isStored bool) error {
                  return addRow(
                      parser.NewDString("def"),                     //table_catalog

Use defString here

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pkg/sql/information_schema.go, line 432 at r1 (raw file):

                  direction string, isStored bool) error {
                  return addRow(
                      parser.NewDString("def"),                     //table_catalog

nit: The comments has traditionally had a space after //

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pkg/sql/information_schema.go, line 447 at r1 (raw file):

              }

              for _, index := range append([]sqlbase.IndexDescriptor{table.PrimaryIndex}, table.Indexes...) {

We have a line length limit of 100 characters.

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pkg/sql/information_schema.go, line 447 at r1 (raw file):

              }

              for _, index := range append([]sqlbase.IndexDescriptor{table.PrimaryIndex}, table.Indexes...) {

See forEachIndexInTable

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pkg/sql/information_schema.go, line 449 at r1 (raw file):

              for _, index := range append([]sqlbase.IndexDescriptor{table.PrimaryIndex}, table.Indexes...) {
                  sequence := 1
                  for i, col := range index.ColumnNames {

This deserves a quick comment. Something like "We add a row for each..."

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pkg/sql/testdata/information_schema, line 667 at r1 (raw file):

## information_schema.statistics
statement ok
CREATE TABLE other_db.cde(id INT PRIMARY KEY, c INT, d INT, e STRING, INDEX idx_c(c), UNIQUE INDEX idx_cd(c,d))

cde?

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Comments from Reviewable

[yznming]

pkg/sql/information_schema.go, line 421 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

Why the quotes?

`collation` is a key word. Create table would execute failed without the quote.

F161027 11:16:38.445281 1 sql/executor.go:289  [startup] syntax error at or near "COLLATION"                                                                       

CREATE TABLE information_schema.statistics (
TABLE_CATALOG STRING NOT NULL DEFAULT '',
TABLE_SCHEMA STRING NOT NULL DEFAULT '',
TABLE_NAME STRING NOT NULL DEFAULT '',
NON_UNIQUE BOOL NOT NULL DEFAULT FALSE,
INDEX_SCHEMA STRING NOT NULL DEFAULT '',
INDEX_NAME STRING NOT NULL DEFAULT '',
SEQ_IN_INDEX INT NOT NULL DEFAULT 0,
COLUMN_NAME STRING NOT NULL DEFAULT '',
COLLATION STRING NOT NULL DEFAULT '',
^

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*Comments from [Reviewable](https://reviewable.io:443/reviews/cockroachdb/cockroach/10220)*
<!-- Sent from Reviewable.io -->

[yznming]

pkg/sql/testdata/information_schema, line 667 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

cde?

sorry, it doesn't means 'Color Doppler Energy' here. I would change the table name .

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Comments from Reviewable

[nvanbenschoten]

other than the one final comment. Thanks!

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Review status: 0 of 2 files reviewed at latest revision, 8 unresolved discussions, all commit checks successful.

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pkg/sql/information_schema.go, line 321 at r2 (raw file):

                  }
                  for _, col := range index.StoreColumnNames {
                      // We add a row for each column of index

"for each stored column"

also, punctuation is needed here and above.

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Comments from Reviewable