[docs] [migrate] changes to import and export sections using the COPY command.

docs/content/preview/migrate/manual-import/_index.md

@@ -2,9 +2,9 @@
 title: Manual import
 headerTitle: Manual import
 linkTitle: Manual import
-description: Migrate PostgreSQL data to YugabyteDB.
+description: Manual PostgreSQL import to YugabyteDB.
 image: /images/section_icons/develop/learn.png
-headcontent: Migrate PostgreSQL data to YugabyteDB using ysql_dump.
+headcontent: Manual PostgreSQL import to YugabyteDB.
 aliases:
   - /preview/migrate/migrate-from-postgresql/
 menu:
@@ -17,11 +17,18 @@ type: indexpage
 
 The steps below cover how to manually migrate PostgreSQL data and applications to YugabyteDB.
 
+- [Convert a PostgreSQL schema](migrate-schema/)
+- [Migrate a PostgreSQL application](migrate-application/)
+- [Export PostgreSQL data](export-data/)
+- [Prepare a cluster](prepare-cluster/)
+- [Import PostgreSQL data](import-data/)
+- [Verify a migration](verify-migration/)
+
 {{< tip title="Migrate using YugabyteDB Voyager" >}}
 To automate your migration from PostgreSQL to YugabyteDB, use [YugabyteDB Voyager](../yb-voyager/).
 {{< /tip >}}
 
-<div class="row">
+<!-- <div class="row">
 
   <div class="col-12 col-md-6 col-lg-12 col-xl-6">
     <a class="section-link icon-offset" href="migrate-schema/">
@@ -107,4 +114,4 @@ To automate your migration from PostgreSQL to YugabyteDB, use [YugabyteDB Voyage
     </a>
   </div>
 
-</div>
+</div> -->

docs/content/preview/migrate/manual-import/export-data.md

@@ -13,7 +13,90 @@ menu:
 type: docs
 ---
 
-The recommended way to export data from PostgreSQL for purposes of importing it to YugabyteDB is using the CSV format.
+
+The recommended way to export data from PostgreSQL for purposes of importing it to YugabyteDB is via CSV files using the COPY command.
+However, for exporting an entire database that consists of smaller datasets, you can use the YugabyteDB [`ysql_dump`](../../../admin/ysql-dump/) utility.
+
+{{< tip title="Migrate using YugabyteDB Voyager" >}}
+To automate your migration from PostgreSQL to YugabyteDB, use [YugabyteDB Voyager](../../yb-voyager/). To learn more, refer to the [export schema](../../yb-voyager/migrate-steps/#export-and-analyze-schema) and [export data](../../yb-voyager/migrate-steps/#export-data) steps.
+{{< /tip >}}
+
+## Export data into CSV files using the COPY command
+
+To export the data, connect to the source PostgreSQL database using the psql tool, and execute the COPY TO command as follows:
+
+```sql
+COPY <table_name>
+    TO <table_name>.csv
+    WITH (FORMAT CSV DELIMITER ',' HEADER);
+```
+
+{{< note title="Note" >}}
+
+The COPY TO command exports a single table, so you should execute it for every table that you want to export.
+
+{{< /note >}}
+
+It is also possible to export a subset of rows based on a condition:
+
+```sql
+COPY (
+    SELECT * FROM <table_name>
+    WHERE <condition>
+)
+TO <table_name>.csv
+WITH (FORMAT CSV DELIMITER ',' HEADER);
+```
+
+For all available options provided by the COPY TO command, refer to the [PostgreSQL documentation](https://www.postgresql.org/docs/current/sql-copy.html).
+
+### Parallelize large table export
+
+For large tables, it might be beneficial to parallelize the process by exporting data in chunks as follows:
+
+```sql
+COPY (
+    SELECT * FROM <table_name>
+    ORDER BY <primary_key_col>
+    LIMIT num_rows_per_export OFFSET 0
+)
+TO '<table_name>_1.csv'
+WITH (FORMAT CSV DELIMITER ',' HEADER);
+```
+
+```sql
+COPY (
+    SELECT * FROM <table_name>
+    ORDER BY <primary_key_col>
+    LIMIT num_rows_per_export OFFSET num_rows_per_export
+)
+TO '<table_name>_2.csv'
+WITH (FORMAT CSV DELIMITER ',' HEADER);
+```
+
+```sql
+COPY (
+    SELECT * FROM <table_name>
+    ORDER BY <primary_key_col>
+    LIMIT num_rows_per_export OFFSET num_rows_per_export * 2
+)
+TO '<table_name>_3.csv'
+WITH (FORMAT CSV DELIMITER ',' HEADER);
+```
+
+You can run the above commands in parallel to speed up the process. This approach will also produce multiple CSV files, allowing for parallel import on the YugabyteDB side.
+
+## Export data into SQL script using ysql_dump
+
+An alternative way to export the data is using the YugabyteDB [`ysql_dump`](../../../admin/ysql-dump/) backup utility, which is derived from PostgreSQL pg_dump.
+
+```sh
+$ ysql_dump -d <database_name> > <database_name>.sql
+```
+
+`ysql_dump` is the ideal option for smaller datasets, because it allows you to export a whole database by running a single command. However, the COPY command is recommended for large databases, because it significantly enhances the performance.
+
+<!--
 
 ## Exporting an entire database
 
@@ -66,4 +149,4 @@ COPY (
 ) TO 'export-2.csv' WITH CSV;
 
 ...
-```
+``` -->

docs/content/preview/migrate/manual-import/import-data.md

@@ -13,28 +13,92 @@ menu:
 type: docs
 ---
 
-The next step is to import the PostgreSQL data into YugabyteDB.
+{{< tip title="Migrate using YugabyteDB Voyager" >}}
+To automate your migration from PostgreSQL to YugabyteDB, use [YugabyteDB Voyager](../../yb-voyager/). To learn more, refer to the [import schema](../../yb-voyager/migrate-steps/#import-schema) and [import data](../../yb-voyager/migrate-steps/#import-data) steps.
+{{< /tip >}}
 
-{{< note title="Note" >}}
-After the data import step, remember to recreate any constraints and triggers that might have been disabled to speed up loading the data. This would ensure that the database will perform relational integrity checking for data going forward.
-{{< /note >}}
+## Import data from CSV files
+
+To import data that was previously exported into CSV files, use the COPY FROM command as follows:
+
+```sql
+COPY <table_name>
+    FROM ‘<table_name>.csv’
+    WITH (
+        FORMAT CSV DELIMITER ',' HEADER
+        ROWS_PER_TRANSACTION 1000
+        DISABLE_FK_CHECK
+    );
+```
+
+In the command above, the `ROWS_PER_TRANSACTION` parameter splits the load into smaller transactions (1000 rows each in this example), instead of running a single transaction spawning across all the data in the file. Additionally, the `DISABLE_FK_CHECK` parameter skips the foreign key checks for the duration of the import process.
+
+Both `ROWS_PER_TRANSACTION` and `DISABLE_FK_CHECK` parameters are recommended for the initial import of the data, especially for large tables, because they significantly reduce the total time required to import the data. You can import multiple files in a single COPY command to further speed up the process. Following is a sample example:
+
+```sql
+yugabyte=# \! ls t*.txt
+t1.txt	t2.txt	t3.txt
+
+yugabyte=# \! cat t*.txt
+1,2,3
+4,5,6
+7,8,9
+
+yugabyte=# \d t
+                 Table "public.t"
+ Column |  Type   | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ c1     | integer |           |          |
+ c2     | integer |           |          |
+ c3     | integer |           |          |
 
-## Import a database
+yugabyte=# SELECT * FROM t;
+ c1 | c2 | c3
+----+----+----
+(0 rows)
 
-To import an entire database from a `pg_dump` or `ysql_dump` export, use `ysqlsh`. The command should look as shown below.
+yugabyte=# COPY t FROM PROGRAM 'cat /home/yugabyte/t*.txt' WITH (FORMAT CSV, DELIMITER ',', ROWS_PER_TRANSACTION 1000, DISABLE_FK_CHECK);
+COPY 3
+
+yugabyte=# SELECT * FROM t;
+ c1 | c2 | c3
+----+----+----
+  7 |  8 |  9
+  4 |  5 |  6
+  1 |  2 |  3
+(3 rows)
 
-```sh
-$ ysqlsh -f <db-sql-script>
 ```
 
-{{< tip title="Tip" >}}
-The `ysqlsh` tool is a derivative of the PostgreSQL tool, `psql`. All `psql` commands would work in `ysqlsh`.
-{{< /tip >}}
+For detailed information on the COPY FROM command, refer to the [COPY](../../../api/ysql/the-sql-language/statements/cmd_copy/) statement reference.
 
-## Import a table using COPY FROM
+### Error handling
 
-Importing a single table (or a partial export from a table) can be done by running the COPY FROM command, and providing it the location of the export file prepared in a previous step. This should look as shown below.
+If the COPY FROM command fails during the process, you should try rerunning it. However, you don’t have to rerun the entire file. COPY FROM imports data into rows individually, starting from the top of the file. So if you know that some of the rows have been successfully imported prior to the failure, you can safely ignore those rows by adding the SKIP parameter.
+
+For example, to skip the first 5000 rows in a file, run the command as follows:
 
 ```sql
-COPY country FROM 'export.csv' DELIMITER ',' CSV HEADER;
+COPY <table_name>
+    FROM ‘<table_name>.csv’
+    WITH (
+        FORMAT CSV DELIMITER ',' HEADER
+        ROWS_PER_TRANSACTION 1000
+        DISABLE_FK_CHECK
+        SKIP 5000
+    );
 ```
+
+## Import data from SQL script
+
+To import an entire database from a `pg_dump` or `ysql_dump` export, use `ysqlsh` as follows:
+
+```sql
+ysqlsh -f <database_name>.sql
+```
+
+{{< note title="Note" >}}
+
+After the data import step, remember to recreate any constraints and triggers that might have been disabled to speed up loading the data. This ensures that the database will perform relational integrity checking for data going forward.
+
+{{< /note >}}